[llvm] [Support] [Debuginfo] Add http and debuginfod client libraries and llvm-debuginfod-find tool

[noajshu]

Summary

This patch implements debuginfod and http client libraries with local caching. A few unit and lit tests are included.
The client libraries are only built if the cmake configuration flag is passed:
cmake [...] -DLLVM_ENABLE_DEBUGINFOD_CLIENT=1
LibCURL is required to build the clients.
The standalone tool llvm-debuginfod-find is also provided; it wraps the debuginfod client library.
The lit tests specific to this tool can be run e.g. with:
LIT_FILTER='.*llvm-debuginfod.*' ninja -C build check-llvm
Thanks in advance for comments and critiques!

This has been split into the following sub-diffs:

• D112751
• D112753
• D112758
• D112759

[phosek]

llvm/lib/Debuginfod/Debuginfod.cpp

39

Nit: no empty line.

43–52

This could be a switch.

81

Nit: no empty line.

llvm/lib/Support/HTTPClient.cpp

25

This is still not addressed.

45

This is still not addressed.

53

This is still not addressed.

[noajshu]

Refactor HTTP Client to use std::vector & improve code formatting.

[noajshu]

llvm/lib/Support/HTTPClient.cpp

25

Thanks, I have refactored to use std::vector and eliminated casts entirely.

[noajshu]

rebase against main

[phosek]

llvm/lib/Support/HTTPClient.cpp

32

One potential downside of this approach is you may have to resize the buffer multiple times as the data comes in which would be inefficient.

I was reading about alternatives, one possibility would be check a priori what's the size of the resource you're fetching is by performing a HEAD request (via CURLOPT_NOBODY and CURLOPT_HEADER set to 1) asking for the HTTP headers to be written via CURLOPT_WRITEHEADER and CURLOPT_WRITEFUNCTION and parsing the Content-Length value. Then you can allocate an appropriately sized buffer and fetch the actual content. You might even use WritableMemoryBuffer::getNewUninitMemBuffer instead of std::vector since you don't need to resize.

[noajshu]

Replaced lit.util.pythonize_bool with llvm_canonicalize_cmake_booleans in lit.site.cfg.py.in.

[noajshu]

llvm/lib/Support/HTTPClient.cpp

32

Thanks, this is a very interesting idea! I will try to do the same thing using just a single request, by triggering the resize in CURLOPT_HEADERFUNCTION when the content-length is available.

[noajshu]

Parse Content-Length header to avoid HTTP response buffer reallocations, convert HTTP Body to MemoryBuffer.

[noajshu]

Cherry-pick to fix extraneous delete in patch, minor style / formatting changes.

[noajshu]

llvm/lib/Support/HTTPClient.cpp

32

Thanks for this suggestion. I have implemented this single-allocation scheme and switched the HTTP buffer type to a LLVM MemoryBuffer. Please let me know if you have any comments on this. Thanks!

[phosek]

llvm/lib/Support/HTTPClient.cpp

46

We usually also try to provide a message explaining what went wrong: assert(Size == 1 && "...").

51–53

I'd avoid the macros which we don't usually use in C++ and instead use the StringRef methods, so you can do something like:

StringRef Header(Contents, NMemb);
if (Header.starts_with("Content-Length: ")) {
  StringRef Length = Header.substr(16);
  size_t ContentLength;
  if (!Length.getAsInteger(10, ContentLength)) {
    ...
  }
}

We should also make the code more resilient to handle potential issues, for example could the header look like Content-Length : N or is it guaranteed to always be Content-Length: N?

53

If the header doesn't contain Content-Length, would we fail in writeMemoryCallback because we haven't allocated the buffer? I think the should be more resilient to handle that situation somehow (even if just by returning an error).

[noajshu]

Perform Content-Length header parsing with StringRef's startswith_insensitive.
Also made minor formatting changes and remove C macros.

[noajshu]

llvm/lib/Support/HTTPClient.cpp

51–53

Thanks for pointing out the variations in header formatting. I took a look at the HTTP/1.1 specification and changed the parser to use startswith_insensitive as header names are case insensitive as well.
To handle extra whitespace perhaps we could use a case-insensitive regex match like content-length\s*?:\s*?(\d+). This would also give us the digits of the length as a match group.

[noajshu]

Use Regex to parse Content-Length header.
Comments for assertions. Gracefully produce an error if the HTTP response lacks Content-Length header.

[noajshu]

llvm/lib/Support/HTTPClient.cpp

51–53

I have changed this to use a Regex instead of a startswith test.

53

Instead of asserting the buffer has been allocated, I changed it to terminate the download and return an Error. However I agree we ought to be more resilient in this case especially since Transfer-Encoding is a valid alternative to Content-Length.
Perhaps we could fall back to repeated re-allocations in the case there is no Content-Length header?

[noajshu]

Gracefully fall back to std::vector buffer if Content-Length is not specified in HTTP response.
Note that this is ~24x slower for a 3GB download. libCURL executes the callback once per 1KB on average.
Also moved static callback functions and OffsetBuffer inside an anonymous namespace in HTTPClient.cpp.

[noajshu]

llvm/lib/Support/HTTPClient.cpp

53

The latest diff handles a missing Content-Length by falling back to a std::vector buffer. This has the disadvantage of a resize on each write callback and an additional allocation + copy to convert to the returned MemoryBuffer. In my test it downloads ~24x slower without the Content-Length header.

[phosek]

llvm/lib/Support/HTTPClient.cpp

52

According to the spec, Content-Length is the only acceptable spelling so I think we could be a little more strict here and require that particular case.

92

Is it possible to use StringRef::getAsInteger instead?

llvm/test/tools/llvm-debuginfod/find-debuginfod-asset.py

8–12 ↗

(On Diff #380544)

I'd consider using argparse and give the arguments more descriptive names.

33 ↗

(On Diff #380544)

The path of the tool should be passed as a variable to this script from the test (which should get it as a lit substitution from CMake). Otherwise, you might accidentally pick up the system version which is undesirable.

llvm/test/tools/llvm-debuginfod/llvm-debuginfod-find.test

3

This would ideally be a substitution.

llvm/tools/llvm-debuginfod/llvm-debuginfod-find.cpp

72–80

I think this should use XDG_CACHE_HOME when set instead (which typically defaults to $HOME/.cache), see https://specifications.freedesktop.org/basedir-spec/basedir-spec-latest.html. We should also check what the macOS and Windows alternatives are. This implementation should only be used as a fallback.

llvm/unittests/Debuginfod/DebuginfodTests.cpp

14

I don't think this is a particularly useful test, but we should be able to improve this once we also have a server.

llvm/unittests/Support/HTTPClient.cpp

16

Ditto for this one.

[phosek]

In D111252#3071626, @noajshu wrote:

Gracefully fall back to std::vector buffer if Content-Length is not specified in HTTP response.
Note that this is ~24x slower for a 3GB download. libCURL executes the callback once per 1KB on average.
Also moved static callback functions and OffsetBuffer inside an anonymous namespace in HTTPClient.cpp.

Given that Content-Length is really required for efficient reads, I think we should consider it mandatory and treat its absence as a protocol error rather than providing an inefficient fallback.

This is what clangd does as well, see https://github.com/llvm/llvm-project/blob/8189c4eee74959882f4f31c6c5f969cec5cca7eb/clang-tools-extra/clangd/JSONTransport.cpp#L242. You could also use that implementation as an inspiration for how to parse the header using LLVM libraries and avoid regular expressions.

[noajshu]

Generalize / rewrite lit testing script to handle multiple clients and servers and simplify content-length parsing + HTTP buffer allocation.

[noajshu]

llvm/lib/Support/HTTPClient.cpp

52

Agreed, it seems a safe bet and is much simpler than using a regex. I've switched it out to use nearly the exact same Content-Length parsing as clangd.

92

Switched to use the clangd style parser which uses llvm::getAsUnsignedInteger.

llvm/test/tools/llvm-debuginfod/llvm-debuginfod-find.test

3

Thanks, I didn't realize this wasn't being expanded! I added the tool name in llvm/test/lit.cfg.py so that it gets substituted with the full path. If you'd like I can make this more explicit by using a % prefix and ToolSubst.

[noajshu]

Use $XDG_DATA_HOME to set cache dir, fall back to $HOME and then current directory.

[noajshu]

Use sys::path::cache_directory to find where to put cached debuginfod assets.

[noajshu]

llvm/tools/llvm-debuginfod/llvm-debuginfod-find.cpp

72–80

Thanks, I've switched it out to use LLVM's platform-independent cache_directory function, which in turn uses XDG_CACHE_HOME where applicable.

[phosek]

llvm/test/tools/llvm-debuginfod/client-server-test.py

57–108 ↗

(On Diff #380822)

I'd move this to a main function which is more conventional.

[labath]

Let me just say outright that I don't feel qualified to say whether this belongs in llvm (I think it does) or not, so I am not going to click approve no matter how well you respond to my comments. However, I do have some experience with sockets and funky tests, so I think I can say something useful about those aspects of the patch.

llvm/lib/Debuginfod/Debuginfod.cpp

2–3

wrap fail

llvm/lib/Support/CMakeLists.txt

79

Who sets CURL_LIBRARIES ?

llvm/lib/Support/HTTPClient.cpp

16–24

This isn't super important, but the best way to ensure you follow the rules for include ordering, is to put them in a single block (with no empty lines), as then clang-format will order them for you.

35

The anonymous namespace should end here, and the rest should be static functions, per https://llvm.org/docs/CodingStandards.html#anonymous-namespaces

120–121

This isn't explicitly spelled out anywhere (and probably not used entirely consistently), but I believe the prevalent style, and one most consistent with the "make namespaces as small as possible" in the anonymous namespace section is to slap a using namespace llvm; at the start of the file, and then to explicitly prefix with llvm:: the header functions that you're defining.

llvm/test/tools/llvm-debuginfod/client-server-test.py

23 ↗

(On Diff #380822)

Can we get rid of these sleeps? Like, maybe the server could somehow signal (create a file, write to stdout/other fd, ...) that it has initialized and is ready to serve)..

I can speak from experience that getting sleep-based tests to work correctly is very tricky. You need to set the timeout very high to ensure you cover the final 0.01 percentile, and when you do that, you end up needlessly slowing down the other 99.99% of the test runs.

llvm/test/tools/llvm-debuginfod/llvm-debuginfod-find.test

2

Since, presumably, every test in this folder is going to have this clause, it would be better to do this via a lit.local.cfg file.

5

There's absolutely no chance this will pass reliably with a hard-coded port. You'll need a mechanism to select a free port at runtime. You can do that by passing port 0 to http.server.HTTPServer and then fetching the actual port via instance.server_port.

This can then be combined with the sleep comment, as you can take the notification of the listening port as a positive acknowledgement that the server is ready to accept connections.

6–14

I don't think this is a good way to design a test. I expect it will be very hard (or outright impossible) to get this working on windows because of the differences in quoting behavior. I'd recommend a pattern like:

RUN: python %S/client-server-test.py %s

// Or the server could be started automatically, possibly within the same process, as that makes it easier to pass the actual port number
SERVER: ???

// DEBUGINFOD_URLS can probably be set automatically
CLIENT: llvm-debuginfod-find fake_build_id --executable
CLIENT: llvm-debuginfod-find fake_build_id --source /directory/file.c
...

Only the RUN stanza would be parsed by lit. The rest would be processed by the python script. The thing you lose this way is the built-in lit substitutions (they'll only work on the RUN line), but it's not clear to me how useful would those actually be. OTOH, this means you can implement custom substitutions, tailored to your use case.

If you're going to have a lot of these tests, you could also consider implementing a custom test format, which would give you an even greater flexibility on how to write and run these tests, but that's probably premature at this point.

(BTW: The # in front of all the lines is completely redundant. The reason it's normally present is because test file is also a valid source file for some language, but that is not the case here.)

llvm/tools/llvm-debuginfod/CMakeLists.txt

10

What's the purpose of this?

llvm/tools/llvm-debuginfod/llvm-debuginfod-find.cpp

77

s/!size()/empty()

79

When does the current directory fallback kick in? Is it actually useful? Should you exit instead?

93

llvm_unreachable is not appropriate for user error (wrong command line arguments).

llvm/unittests/Support/HTTPClient.cpp

16

This would be better done as EXPECT_THAT_EXPECTED(httpGet(...), Failed<StringError>()) or even FailedWithMessage("whatever"), though I agree that this is not very useful.

I think the interesting question is whether we're ok with not having any coverage for the lower level apis, and I'm not really sure what the answer to that is.

[noajshu]

llvm/lib/Support/CMakeLists.txt

79

When LLVM_ENABLE_CURL is on, llvm/cmake/config-ix.cmake calls find_package(CURL) which sets the CURL_LIBRARIES. This was added in D111238.

llvm/lib/Support/HTTPClient.cpp

16–24

That's a great tip, thanks!

35

Thanks!

llvm/tools/llvm-debuginfod/CMakeLists.txt

10

Good catch, this is no longer required.

llvm/tools/llvm-debuginfod/llvm-debuginfod-find.cpp

79

The fallback would kick in when cache_directory comes up empty-handed. This can happen on linux if neither $XDG_CACHE_HOME nor $HOME are in the environment. I would have no problem with removing the fallback and failing in this case as the user can always specify the current directory using --cache-dir anyways.

[noajshu]

llvm/unittests/Support/HTTPClient.cpp

16

Thanks, updated!
I agree with the comments that these unit tests are not adding much value. One option until we have a server in llvm would be to GET http://llvm.org, although that does require an internet connection. By the lower level APIs, are you referring to the static callback functions used to implement httpGet, or to the CURL library itself?

[noajshu]

Remove cache dir fallback to current directory in debuginfod-find.
Use EXPECT_THAT_EXPECTED in unit tests, switch functions out of anonymous namespaces (use static instead)

[noajshu]

Make namespaces smaller by switching library implementations to use using namespace llvm; and llvm:: prefixing.

[labath]

llvm/CMakeLists.txt

975–977

Why isn't this next to the other llvm_canonicalize_cmake_booleans calls?

(It would also help if you upload the full context with your patch (arcanist does it automatically, and you can achieve it with git diff -U9999 if you do it manually).

llvm/include/llvm/Debuginfod/Debuginfod.h

37

Small strings are typically not returned by value, and I don't think that the performance of this is particularly critical (if it was, you'd probably use a SmallVectorImpl<char>& by-ref argument), so I'd probably use a std::string here.

llvm/lib/Support/CMakeLists.txt

79

I see. In that case, I think it would be good to also add set(LLVM_ENABLE_CURL ... CACHE) somewhere, so that this appears as a user-settable value in UIs and such.

llvm/tools/llvm-debuginfod/llvm-debuginfod-find.cpp

79

an unset HOME variable is going to be most likely an accident, and i think the usage of CWD would be surprising in that case. So, I'd leave the fallback out, but this is your tool, so I'm going to leave that up to you.

111

it seems #undef DEBUG_TYPE is rarely used in cpp files (headers are a different story), and when it is, it's usually because it's #defined to a different files immediately afterwards. Undefining at the end of a file seems pointless.

llvm/unittests/Support/HTTPClient.cpp

16

I mean the httpGet function itself -- we generally don't test private implementation details (directly).
In an ideal world I'd split this patch into two (or even three, with the first part being the introduction of httpGet), and each would come with it's own tests. Testing the error message is nice to have, but it just scratches the surface. In httpGet, the content-length handling seems interesting to test, for example.

But yes, you'd need some way to create/mock the server connection for that to work...

[noajshu]

Add debuginfod-find.test which is simpler and less general-purpose, and does not require special command-line quoting behavior or JSON configuration.
This test incorporates Pavel's suggestion to assign the port to the first available, and avoids using timing to orchestrate the client and server. This would replace the llvm-debuginfod-find.test + client-server-test.py scheme.

[noajshu]

Only use llvm_canonicalize_cmake_boolean where it's needed, in llvm/test/CMakeLists.txt with the other invocations.

[noajshu]

llvm/CMakeLists.txt

975–977

Thanks and just moved this!

[noajshu]

Remove old end-to-end tests and add LLVM_ENABLE_CURL cmake variable cache string.

[noajshu]

Various style and usability updates.
Remove use of llvm_unreachable in handling user error, extraneous #undef DEBUG_TYPE, add Cmake cache vars, remove CWD fallback for cache dir.

[noajshu]

fetchDebuginfo returns a std::string instead of small string.

[labath]

llvm/test/tools/llvm-debuginfod/debuginfod-find.test

1–2 ↗

(On Diff #381368)

This seems fine for now, though if you start having more of these, it would definitely be good to factor some of this out.

You can consider renaming the file to .py to get syntax highlighting.

21 ↗

(On Diff #381368)

Where will this be storing the downloaded files? It should probably be %t or some derivative. And you should clean the folder before the test.

28–29 ↗

(On Diff #381368)

The way this is written now, the test would pass if I replaced debuginfod-find with /bin/true. Is there anything else you can check here?

llvm/tools/llvm-debuginfod/llvm-debuginfod-find.cpp

95

You're only checking that the user specified _at least_ one of the arguments.

[noajshu]

Refactor HTTP Client (Curl wrapper).
This refactor enabled writing more meaningful unit tests and fixes several bugs in the client.

[noajshu]

Workaround for unit tests, to avoid need for parent's destructor to invoke child's override.
There is a more general explanation of why this does not work here: more details here

[noajshu]

llvm/unittests/Support/HTTPClient.cpp

16

Hi Pavel, first off thanks for all of your comments. I refactored the HTTP client to enable meaningful unit tests. It's now split into two new class hierarchies rooted at HTTPRequest and HTTPResponseHandler. This way CURL can be swapped out with a a different HTTP backend, including a simulated backend during unit testing.
Similarly, the buffered response handler can be unit tested in isolation without data going through a socket. This allows some nontrivial tests of how it handles content-lengths.
I am very interested in your thoughts on this refactor, and if you have ideas for other unit tests of the HTTP client or feedback on the ones here. I wonder if it makes sense to refactor the Debuginfod client library as well to enable more meaningful unit tests there. And please feel free to suggest a different approach if you feel the refactor moves us in the wrong direction.

For now I will work on addressing your comments on the other areas of the diff.
Since it is even larger now, it could certainly make sense to split off into a few diffs. One way to do this could be:

[diff 0 ] HTTP Client + unit tests
[diff 1] Debuginfod Client library + unit tests
[diff 2] Debuginfod-Find tool + end-to-end (lit) tests

[phosek]

llvm/include/llvm/Support/HTTPClient.h

42

This is unnecessary.

71–94

I'd move the cURL-based implementation into a separate header and source file, for example Support/CURLClient.{h,cpp}. Otherwise, anyone who includes HTTPClient.h automatically pulls in <curl/curl.h> which is undesirable.

72

This is unnecessary.

80–82

Do these need to public?

84–87

Do these need to be public?

96

This function seems unnecessary as it's functionality is now effectively provided by HTTPRequest and HTTPRequestConfig which is more flexible (for example they can potentially support methods other than Get).

llvm/lib/Support/HTTPClient.cpp

78

Rather than printing the error to stderr which may be undesirable for example when using LLVM as a library, I think it'd be better to store the error inside the class (it might be possible to use ErrorList) and then return it from curlPerform.

90

The same here.

104–114

Could this method be inlined directly into CurlHTTPRequest::performRequest?

[labath]

Well... I hate to say it, but I found the version very easy to get lost in. It seems to me you're exposing a lot more implementation details than it is necessary (including the entire curl.h header, which is something we try to avoid. And the fact that tests don't even go through the public interface make it hard to keep track of what is being tested. If we are going to do this, maybe we could use a pattern like this:

class CurlInterface {
  virtual Error init()  = 0;
  virtual Error cleanup() = 0;
  virtual Error perform() = 0;
  virtual void setWriteFunction(...) = 0;
  // etc. 
  // It doesn't have to match the curl interface verbatim. Feel free 
  // to perform basic simplifications and c++-ifications of the 
  // interface. You'll need to do some of those to avoid dependence 
  // on curl.h anyway.
};

Expected<HTTPResponseBuffer> httpGet(const Twine &Url, CurlInterface &curl);
Expected<HTTPResponseBuffer> httpGet(const Twine &Url); // calls the first function with the default/real curl implementation

This shouldn't expose too much implementation details, and this interface could even conceivably by useful by someone who wants to use a custom http-ish library/transport/thingy.

Then, in the test, you could use gmock to program a fake curl implementation:

class CurlMock: public CurlInterface {
  MOCK_METHOD0(init, Error());
  ...
};

TEST(httpGet, whatever) {
  CurlMock curl;
  EXPECT_CALL(curl, setWriteFunction).WillOnce(SaveArg<0>(&writeFunc));
  EXPECT_CALL(curl, perform).WillOnce([&] {
    EXPECT_THAT_ERROR(writeFunc(...), llvm::Succeeded());
    EXPECT_THAT_ERROR(writeFunc(...), llvm::Failed());
    ...
    return llvm::Error::success();
  });
  EXPECT_THAT_ERROR(httpGet("http://foo", curl), llvm::Succeeded())
}

How does that sound?

llvm/lib/Support/HTTPClient.cpp

69

the llvm:: qualifications are not necessary here

139

drop .str().str(), it's cleaner

llvm/unittests/Support/HTTPClient.cpp

16

Yeah, if we're going to have tests for each of these components, I'd definitely recommend splitting them out into separate patches.

[noajshu]

Add CurlHTTPRequest::ErrorState using ErrorList to track errors during curl http request lifecycle.
Also miscellaneous style updates, redundant namespace qualifiers.

[noajshu]

llvm/lib/Support/HTTPClient.cpp

78

Great idea, I've added this and removed the prints to stderr. The ErrorState will also surface for other Error-returning methods of CurlHTTPRequest.

[noajshu]

Updates to CurlHTTPRequest access specifiers.

[noajshu]

Remove extraneous curlPerform method from CurlHTTPRequest

[noajshu]

Remove httpGet function.

[noajshu]

Improvements to regression (lit) tests.
Use %t as the asset cache directory and clean up directory before each test. Verify local file contents match expected contents.

[noajshu]

Split out CurlHTTPRequest into CURLClient.{h,cpp}.

[noajshu]

Rebase against main.

[noajshu]

@labath Thank you for your helpful feedback on this diff!
I have split into 4 sub-diffs. The HTTP client/request/response handler architecture is in D112751 and the curl client is in D112753. Could we continue the discussion there?

llvm/include/llvm/Support/HTTPClient.h

80–82

Nope -- updated most to private, and curlInit to protected (for unit testing).

84–87

The curlHandle{HeaderLine,BodyChunk} method is invoked by the static curl{HeaderLine,BodyChunk}MethodHook function, which then needs access.

I tried instead having curl directly call back to a private method, but then the implicit this argument is replaced by the first parameter passed by curl, which is the pointer to the header/body contents.

96

Agreed that this could be removed and on the flexibility point I bet another use case might be a StreamingHTTPResponseHandler. This would be especially nice if the localCache is refactored to allow caching objects chunk-by-chunk -- as then large debuginfo would not hog memory (as with the BufferedHTTPResponseHandler).

[noajshu]

Abandoning due to split into separate patches.

llvm/CMakeLists.txt

if (NOT Z3_FOUND)
     message(FATAL_ERROR "LLVM_ENABLE_Z3_SOLVER cannot be enabled when Z3 is not available.")
   endif()
 
   set(LLVM_WITH_Z3 1)
 endif()
 
 set(LLVM_ENABLE_Z3_SOLVER_DEFAULT "${Z3_FOUND}")
 
+
+set(LLVM_ENABLE_DEBUGINFOD_CLIENT_DEFAULT OFF)
+option(
+  LLVM_ENABLE_DEBUGINFOD_CLIENT
+  "Enable experimental LLVM Debuginfod client library"
+  ${LLVM_ENABLE_DEBUGINFOD_CLIENT_DEFAULT}
+)
 if (LLVM_ENABLE_DEBUGINFOD_CLIENT)
   set(LLVM_WITH_CURL 1)
   set(CURL_LIBRARY "-lcurl")
   find_package(CURL 7.74.0 REQUIRED)
   add_compile_definitions(
     LLVM_ENABLE_DEBUGINFOD_CLIENT
     LLVM_WITH_CURL)
 endif()

 if(LLVM_TARGET_IS_CROSSCOMPILE_HOST)
 # Dummy use to avoid CMake Warning: Manually-specified variables were not used
 # (this is a variable that CrossCompile sets on recursive invocations)
 endif()
 
 if( ${CMAKE_SYSTEM_NAME} MATCHES SunOS )
    # special hack for Solaris to handle crazy system sys/regset.h
    include_directories("${LLVM_MAIN_INCLUDE_DIR}/llvm/Support/Solaris")
 endif( ${CMAKE_SYSTEM_NAME} MATCHES SunOS )
 
 # Make sure we don't get -rdynamic in every binary. For those that need it,
 # use export_executable_symbols(target).
 set(CMAKE_SHARED_LIBRARY_LINK_CXX_FLAGS "")
 
 include(AddLLVM)
 include(TableGen)
 
 include(LLVMDistributionSupport)
 

llvm/include/llvm/Debuginfod/Debuginfod.h

+//===-- llvm/Support/Debuginfod.h - Debuginfod client library ---*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file contains the declarations of the debuginfod::fetchInfo
+/// function which can retrieve debugging information from a
+/// debuginfod server, and the debuginfod::AssetType enum class
+///
+///
+//===----------------------------------------------------------------------===//
+
+#ifdef LLVM_ENABLE_DEBUGINFOD_CLIENT
+
+#ifndef LLVM_SUPPORT_DEBUGINFOD_H
+#define LLVM_SUPPORT_DEBUGINFOD_H
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Error.h"
+
+namespace llvm {
+
+/// DebuginfodAssetType - This enum class specifies the types of
+/// debugging information that can be requested from a debuginfod
+/// server.
+enum class DebuginfodAssetType { Executable, Debuginfo, Source };
+
+/// DebuginfodAssetCache - This interface provides a file caching mechanism
+/// powered by LLVM's cache pruning. This should probably be replaced with the
+/// ThinLTO caching scheme after a refactor to move the ThinLTO caching to the
+/// support libs
+class DebuginfodAssetCache {
+  StringRef DirectoryPath;
+
+public:
+  DebuginfodAssetCache(StringRef CacheDirectoryPath);
+  Expected<bool> contains(StringRef RelPath);
+  Error add(StringRef Key, StringRef Contents);
+  Error prune();
+  std::string absolutePath(StringRef Key);
+  Expected<std::string> contentsOf(StringRef Key);
+};
+
+Expected<std::string> fetchInfo(ArrayRef<StringRef> DebuginfodUrls,
+                                StringRef CacheDirectoryPath, StringRef BuildID,
+                                DebuginfodAssetType Type,
+                                StringRef Description = "");
+
+} // end namespace llvm
+
+#endif
+
+#endif

llvm/include/llvm/Support/HTTPClient.h

+//===-- llvm/Support/HTTPClient.h - HTTP client library ---*- C++ -------*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file contains the declarations of the HTTPResponse struct
+/// and httpGet function.
+///
+///
+//===----------------------------------------------------------------------===//
+
+#ifdef LLVM_WITH_CURL
+
+#ifndef LLVM_SUPPORT_HTTP_CLIENT_H
+#define LLVM_SUPPORT_HTTP_CLIENT_H
+
+#include "llvm/Support/Error.h"
+
+namespace llvm {
+struct HTTPResponse {
+  long Code = 0;
+  std::string Body;
+};
+Expected<HTTPResponse> httpGet(const Twine &Url);
+} // end namespace llvm
+
+#endif // LLVM_HTTP_CLIENT_H
+
+#endif

llvm/lib/CMakeLists.txt

 include(LLVM-Build)
 
 # `Demangle', `Support' and `TableGen' libraries are added on the top-level
 # CMakeLists.txt
 
 add_subdirectory(IR)
 add_subdirectory(FuzzMutate)
 add_subdirectory(FileCheck)
 add_subdirectory(InterfaceStub)
 add_subdirectory(IRReader)
 add_subdirectory(CodeGen)
 add_subdirectory(BinaryFormat)
 add_subdirectory(Bitcode)
 add_subdirectory(Bitstream)
+add_subdirectory(Debuginfod)
 add_subdirectory(DWARFLinker)
 add_subdirectory(Extensions)
 add_subdirectory(Frontend)
 add_subdirectory(Transforms)
 add_subdirectory(Linker)
 add_subdirectory(Analysis)
 add_subdirectory(LTO)
 add_subdirectory(MC)

llvm/lib/Debuginfod/CMakeLists.txt

+add_llvm_component_library(LLVMDebuginfod
+  Debuginfod.cpp
+
+  ADDITIONAL_HEADER_DIRS
+  ${LLVM_MAIN_INCLUDE_DIR}/llvm/Debuginfod
+
+  LINK_COMPONENTS
+  Support
+  )

llvm/lib/Debuginfod/Debuginfod.cpp

+//===-- llvm/Support/Debuginfod.cpp - Debuginfod client library -------*- C++
+//-*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+///
+/// This file defines the fetchInfo function, which retrieves
+/// any of the three supported asset types: (executable, debuginfo, source file)
+/// associated with a build-id from debuginfod servers. If a source file is to
+/// be fetched, its absolute path must be specified in the Description argument
+/// to fetchInfo.
+///
+//===----------------------------------------------------------------------===//
+
+#ifdef LLVM_ENABLE_DEBUGINFOD_CLIENT
+
+#include "llvm/Debuginfod/Debuginfod.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/CachePruning.h"
+#include "llvm/Support/Error.h"
+#include "llvm/Support/FileUtilities.h"
+#include "llvm/Support/HTTPClient.h"
+
+#include <sstream>
+
+namespace llvm {
+
+using namespace sys::fs;
+using namespace sys::path;
+
+#define DEBUG_TYPE "DEBUGINFOD"
+
+DebuginfodAssetCache::DebuginfodAssetCache(StringRef CacheDirectoryPath) {
+  DirectoryPath = CacheDirectoryPath;
+}
+
+Expected<bool> DebuginfodAssetCache::contains(StringRef Key) {
+
+  // We prune the cache before answering each query.
+  if (Error Err = prune())
+    return Err;
+
+  auto AbsolutePath = absolutePath(Key);
+  file_status Status;
+  auto EC = status(AbsolutePath, Status);
+  if (EC && EC != errc::no_such_file_or_directory)
+    return createStringError(EC, "failed to check asset cache entry status");
+  else if (EC == errc::no_such_file_or_directory)
+    return false;
+  else
+    return exists(Status);
+}
+
+Error DebuginfodAssetCache::add(StringRef Key, StringRef Contents) {
+  auto AbsolutePath = absolutePath(Key);
+  StringRef Root = parent_path(AbsolutePath);
+
+  // We do not assume the cache directory exists so we must create it.
+  std::error_code EC = create_directories(Root);
+  if (EC)
+    return createStringError(errc::io_error,
+                             "failed to create cache directory path");
+
+  if (Error Err = prune())
+    return Err;
+
+  return writeFileAtomically("llvm-debuginfod-%%%%%%%%%%%%%%%%%%", AbsolutePath,
+                             Contents);
+}
+
+Error DebuginfodAssetCache::prune() {
+  // see CachePruning.h
+  // "A default constructed CachePruningPolicy
+  // provides a reasonable default policy."
+  pruneCache(DirectoryPath, CachePruningPolicy());
+  return Error::success();
+}
+
+static Expected<std::string> contentsOfFile(StringRef AbsolutePath) {
+
+  uint64_t FileSize;
+  if (auto EC = file_size(AbsolutePath, FileSize))
+    return createStringError(EC, "error getting file size");
+
+  LLVM_DEBUG(dbgs() << "got file size of " << FileSize << " bytes\n";);
+
+  LLVM_DEBUG(dbgs() << "opening native file at " << AbsolutePath << "\n";);
+  auto FileOrErr = openNativeFileForRead(AbsolutePath);
+  if (Error Err = FileOrErr.takeError())
+    return Err;
+  auto &File = *FileOrErr;
+  LLVM_DEBUG(dbgs() << "native file opened\n";);
+
+  LLVM_DEBUG(dbgs() << "reading native file\n";);
+  std::vector<char> Buf(FileSize);
+  auto SizeReadOrErr =
+      readNativeFile(File, MutableArrayRef<char>(Buf.data(), Buf.size()));
+  if (Error Err = SizeReadOrErr.takeError())
+    return Err;
+  LLVM_DEBUG(dbgs() << "read native file\n";);
+
+  auto &SizeRead = *SizeReadOrErr;
+  LLVM_DEBUG(dbgs() << "SizeRead = " << SizeRead << " bytes\n";);
+
+  if (SizeRead != FileSize)
+    return createStringError(errc::result_out_of_range,
+                             "failed to read entire file");
+
+  if (auto EC = closeFile(File))
+    return createStringError(EC, "error closing file");
+
+  return std::string(Buf.data(), Buf.size());
+}
+
+Expected<std::string> DebuginfodAssetCache::contentsOf(StringRef Key) {
+  auto AbsolutePath = absolutePath(Key);
+  return contentsOfFile(AbsolutePath);
+}
+
+static std::string hexEncode(std::string String) {
+  std::string Output = "";
+  const std::vector<std::string> hexDigits = {"0", "1", "2", "3", "4", "5",
+                                              "6", "7", "8", "9", "a", "b",
+                                              "c", "d", "e", "f"};
+  for (auto c : String) {
+    unsigned int i1 = (int)c & 0b1111;
+    unsigned int i2 = (int)c >> 4;
+    Output += hexDigits.at(i1);
+    Output += hexDigits.at(i2);
+  }
+  return Output;
+}
+
+std::string DebuginfodAssetCache::absolutePath(StringRef Key) {
+  LLVM_DEBUG(dbgs() << "getting absolute path of " << Key << "\n";);
+  std::string HexEncodedKey = hexEncode(Key.str());
+  auto AbsPath = DirectoryPath + "/llvmcache-debuginfod-" + HexEncodedKey;
+  LLVM_DEBUG(dbgs() << "HexEncodedKey = " << HexEncodedKey << "\n";);
+  LLVM_DEBUG(dbgs() << "got absolute path " << AbsPath << "\n";);
+  return AbsPath.str();
+}
+
+Expected<std::string> fetchInfo(ArrayRef<StringRef> DebuginfodUrls,
+                                StringRef CacheDirectoryPath, StringRef BuildID,
+                                DebuginfodAssetType Type,
+                                StringRef Description) {
+  LLVM_DEBUG(dbgs() << "fetching info, debuginfod urls size = "
+                    << DebuginfodUrls.size() << "\n";);
+  std::string Suffix;
+  if (Type == DebuginfodAssetType::Executable) {
+    Suffix = "executable";
+  } else if (Type == DebuginfodAssetType::Debuginfo) {
+    Suffix = "debuginfo";
+  } else if (Type == DebuginfodAssetType::Source) {
+    // Description is the absolute source path
+    Suffix = "source" + Description.str();
+  } else {
+    llvm_unreachable("invalid debuginfo asset type");
+  }
+
+  DebuginfodAssetCache Cache(CacheDirectoryPath);
+  auto UniqueKey = (BuildID + Suffix).str();
+  auto CacheHitOrErr = Cache.contains(UniqueKey);
+
+  if (Error Err = CacheHitOrErr.takeError())
+    return Err;
+
+  bool &CacheHit = *CacheHitOrErr;
+  if (CacheHit) {
+    LLVM_DEBUG(dbgs() << "cache hit!\n";);
+    return Cache.absolutePath(UniqueKey);
+  }
+
+  // The asset was not found in the local cache, so we must query
+  // the debuginfod servers.
+  for (auto &Url : DebuginfodUrls) {
+
+    Expected<HTTPResponse> ResponseOrErr =
+        httpGet(Url + "buildid/" + BuildID + "/" + Suffix);
+
+    if (Error Err = ResponseOrErr.takeError())
+      return Err;
+
+    HTTPResponse &Resp = *ResponseOrErr;
+    if (Resp.Code == 200) {
+      // We have retrieved the asset from this server,
+      // so we add it to the file cache.
+      if (Error Err = Cache.add(UniqueKey, Resp.Body))
+        return Err;
+
+      // Return the path to the asset on disk.
+      return Cache.absolutePath(UniqueKey);
+    }
+  }
+
+  return createStringError(errc::argument_out_of_domain, "build id not found");
+}
+
+#undef DEBUG_TYPE
+} // namespace llvm
+
+#endif

llvm/lib/Support/CMakeLists.txt

if (MSVC)
   set (delayload_flags delayimp -delayload:shell32.dll -delayload:ole32.dll)
 endif()
 
 # Link Z3 if the user wants to build it.
 if(LLVM_WITH_Z3)
   set(system_libs ${system_libs} ${Z3_LIBRARIES})
 endif()
 
+# Link LibCURL if the user wants it
+if (LLVM_WITH_CURL)
+  set(system_libs ${system_libs} ${CURL_LIBRARIES})
+endif()
+
 # Override the C runtime allocator on Windows and embed it into LLVM tools & libraries
 if(LLVM_INTEGRATED_CRT_ALLOC)
   if (CMAKE_BUILD_TYPE AND NOT ${LLVM_USE_CRT_${uppercase_CMAKE_BUILD_TYPE}} MATCHES "^(MT|MTd)$")
     message(FATAL_ERROR "LLVM_INTEGRATED_CRT_ALLOC only works with /MT or /MTd. Use LLVM_USE_CRT_${uppercase_CMAKE_BUILD_TYPE} to set the appropriate option.")
   endif()
 
   string(REGEX REPLACE "(/|\\\\)$" "" LLVM_INTEGRATED_CRT_ALLOC "${LLVM_INTEGRATED_CRT_ALLOC}")
 
add_llvm_component_library(LLVMSupport
   Compression.cpp
   CRC.cpp
   ConvertUTF.cpp
   ConvertUTFWrapper.cpp
   CrashRecoveryContext.cpp
   DataExtractor.cpp
   Debug.cpp
   DebugCounter.cpp
   DeltaAlgorithm.cpp
   DivisionByConstantInfo.cpp
   DAGDeltaAlgorithm.cpp
   DJB.cpp
   ELFAttributeParser.cpp
   ELFAttributes.cpp
   Error.cpp
   ErrorHandling.cpp
   ExtensibleRTTI.cpp
   FileCollector.cpp
   FileUtilities.cpp
   FileOutputBuffer.cpp
   FoldingSet.cpp
   FormattedStream.cpp
   FormatVariadic.cpp
   GlobPattern.cpp
   GraphWriter.cpp
   Hashing.cpp
+  HTTPClient.cpp
   InitLLVM.cpp
   InstructionCost.cpp
   IntEqClasses.cpp
   IntervalMap.cpp
   ItaniumManglingCanonicalizer.cpp
   JSON.cpp
   KnownBits.cpp
   LEB128.cpp

llvm/lib/Support/HTTPClient.cpp

+//===-- llvm/Support/HTTPClient.cpp - HTTP client library -------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+///
+/// This file defines the httpGet function, implemented using libcurl.
+///
+//===----------------------------------------------------------------------===//
+
+#ifdef LLVM_WITH_CURL
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/Errc.h"
+#include "llvm/Support/Error.h"
+
+#include "llvm/Support/HTTPClient.h"
+
+#include <curl/curl.h>
+
+namespace llvm {
+
+#define DEBUG_TYPE "HTTPClient"
+
+struct MemoryStruct {
+  char *memory;
+  size_t size;
+};
+
+static size_t writeMemoryCallback(void *contents, size_t size, size_t nmemb,
+                                  void *userp) {
+  size_t realsize = size * nmemb;
+  struct MemoryStruct *mem = (struct MemoryStruct *)userp;
+
+  char *ptr = (char *)realloc(mem->memory, mem->size + realsize + 1);
+  if (!ptr) {
+    errs() << "not enough memory (realloc returned NULL)\n";
+    return 0;
+  }
+
+  mem->memory = ptr;
+  memcpy(&(mem->memory[mem->size]), contents, realsize);
+  mem->size += realsize;
+  mem->memory[mem->size] = 0;
+
+  return realsize;
+}
+
+Expected<HTTPResponse> httpGet(const Twine &Url) {
+
+  LLVM_DEBUG(dbgs() << "getting Url " << Url << "\n";);
+
+  struct MemoryStruct chunk;
+
+  chunk.memory = (char *)malloc(1);
+  chunk.size = 0;
+
+  CURL *Curl = curl_easy_init();
+  CURLcode CurlRes;
+  if (!Curl) {
+    return createStringError(errc::io_error, "http library error");
+  }
+
+  std::string UrlString = Url.str();
+  curl_easy_setopt(Curl, CURLOPT_URL, UrlString.c_str());
+  curl_easy_setopt(Curl, CURLOPT_FOLLOWLOCATION, 1L);
+  curl_easy_setopt(Curl, CURLOPT_WRITEFUNCTION, writeMemoryCallback);
+  curl_easy_setopt(Curl, CURLOPT_WRITEDATA, (void *)&chunk);
+
+  LLVM_DEBUG(dbgs() << "performing the curl\n";);
+  CurlRes = curl_easy_perform(Curl);
+  LLVM_DEBUG(dbgs() << "got the CurlRes\n";);
+
+  curl_easy_cleanup(Curl);
+
+  if (CurlRes != CURLE_OK) {
+    free(chunk.memory);
+    return createStringError(errc::io_error, "curl_easy_perform() failed: %s\n",
+                             curl_easy_strerror(CurlRes));
+  }
+
+  std::string Body(chunk.memory, chunk.size);
+  free(chunk.memory);
+  HTTPResponse Resp;
+  Resp.Body = Body;
+  curl_easy_getinfo(Curl, CURLINFO_RESPONSE_CODE, &Resp.Code);
+  return Resp;
+}
+
+#undef DEBUG_TYPE
+
+} // end namespace llvm
+
+#endif

llvm/test/lit.cfg.py

 if config.have_libxml2:
     config.available_features.add('libxml2')
 
 if config.have_opt_viewer_modules:
     config.available_features.add('have_opt_viewer_modules')
 
 if config.expensive_checks:
     config.available_features.add('expensive_checks')
+
+if getattr(config, 'enable_debuginfod_client', False):
+  config.available_features.add('debuginfod_client')

llvm/test/lit.site.cfg.py.in

 @LIT_SITE_CFG_IN_HEADER@
 
+
+# Set attribute value if it is unset.
+def set_default(attr, value):
+  if not getattr(config, attr, None):
+    setattr(config, attr, value)
+
+import lit.util
 import sys
 
 config.host_triple = "@LLVM_HOST_TRIPLE@"
 config.target_triple = "@TARGET_TRIPLE@"
 config.llvm_src_root = path(r"@LLVM_SOURCE_DIR@")
 config.llvm_obj_root = path(r"@LLVM_BINARY_DIR@")
 config.llvm_tools_dir = path(r"@LLVM_TOOLS_DIR@")
 config.llvm_lib_dir = path(r"@LLVM_LIBS_DIR@")

 config.host_os = "@HOST_OS@"
 config.host_cc = "@HOST_CC@"
 config.host_cxx = "@HOST_CXX@"
 # Note: ldflags can contain double-quoted paths, so must use single quotes here.
 config.host_ldflags = '@HOST_LDFLAGS@'
 config.llvm_use_intel_jitevents = @LLVM_USE_INTEL_JITEVENTS@
 config.llvm_use_sanitizer = "@LLVM_USE_SANITIZER@"
 config.have_zlib = @LLVM_ENABLE_ZLIB@
+set_default("enable_debuginfod_client", lit.util.pythonize_bool("@LLVM_ENABLE_DEBUGINFOD_CLIENT@"))
 config.have_libxar = @LLVM_HAVE_LIBXAR@
 config.have_libxml2 = @LLVM_ENABLE_LIBXML2@
 config.have_dia_sdk = @LLVM_ENABLE_DIA_SDK@
 config.enable_ffi = @LLVM_ENABLE_FFI@
 config.build_examples = @LLVM_BUILD_EXAMPLES@
 config.enable_threads = @LLVM_ENABLE_THREADS@
 config.build_shared_libs = @BUILD_SHARED_LIBS@
 config.link_llvm_dylib = @LLVM_LINK_LLVM_DYLIB@

llvm/test/tools/llvm-debuginfod/Inputs/buildid/fake_build_id/debuginfo

+fake_debuginfo

llvm/test/tools/llvm-debuginfod/Inputs/buildid/fake_build_id/executable

+fake_executable

llvm/test/tools/llvm-debuginfod/Inputs/buildid/fake_build_id/source/directory/file.c

+int foo = 0;

llvm/test/tools/llvm-debuginfod/find-test.sh

+set -x
+
+# start the server
+timeout 2s python -m http.server \
+  --directory $1/Inputs/ $3 &
+
+sleep 0.5s
+
+# test the client
+DEBUGINFOD_URLS=http://localhost:$3/ \
+  llvm-debuginfod-find fake_build_id \
+  $2 \
+  -debug
+
+exit

llvm/test/tools/llvm-debuginfod/llvm-debuginfod-find.test

+# REQUIRES: debuginfod_client
+# RUN: bash %S/find-test.sh %S --executable 13573
+# RUN: bash %S/find-test.sh %S --debuginfo 13574
+# RUN: bash %S/find-test.sh %S --source=/directory/file.c 13575

llvm/tools/llvm-debuginfod/CMakeLists.txt

+if (LLVM_ENABLE_DEBUGINFOD_CLIENT)
+  set(LLVM_LINK_COMPONENTS
+    Debuginfod
+    Support
+    )
+  add_llvm_tool(llvm-debuginfod-find
+    llvm-debuginfod-find.cpp
+    )
+  set_property(TARGET llvm-debuginfod-find PROPERTY LLVM_SYSTEM_LIBS ${imported_libs})
+  if(LLVM_INSTALL_BINUTILS_SYMLINKS)
+    add_llvm_tool_symlink(debuginfod-find llvm-debuginfod-find)
+  endif()
+endif()

llvm/tools/llvm-debuginfod/llvm-debuginfod-find.cpp

+//===-- llvm-debuginfod-find.cpp - Simple CLI for libdebuginfod-client ----===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+///
+/// \file
+/// This file contains the llvm-debuginfod-find tool. This tool
+/// queries the debuginfod servers in the DEBUGINFOD_URLS environment
+/// variable (delimited by space (" ")) for the executable,
+/// debuginfo, or specified source file of the binary matching the
+/// given build-id.
+///
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Config/config.h"
+#include "llvm/Debuginfod/Debuginfod.h"
+#include "llvm/Option/Arg.h"
+#include "llvm/Option/ArgList.h"
+#include "llvm/Option/Option.h"
+#include "llvm/Support/COM.h"
+#include "llvm/Support/CommandLine.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/Errc.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/InitLLVM.h"
+#include "llvm/Support/Path.h"
+#include "llvm/Support/StringSaver.h"
+#include "llvm/Support/raw_ostream.h"
+#include <algorithm>
+#include <cstdio>
+#include <cstring>
+#include <string>
+
+#define DEBUG_TYPE "llvm-debuginfod-find"
+
+using namespace llvm;
+
+cl::opt<std::string> InputBuildID(cl::Positional, cl::Required,
+                                  cl::desc("<input build_id>"), cl::init("-"));
+
+static cl::opt<bool>
+    FetchExecutable("executable", cl::init(false),
+                    cl::desc("fetch the associated executable"));
+
+static cl::opt<bool> FetchDebuginfo("debuginfo", cl::init(false),
+                                    cl::desc("fetch associated debuginfo"));
+
+static cl::opt<std::string> FetchSource("source", cl::init(""),
+                                        cl::desc("/filename"));
+
+ExitOnError ExitOnErr;
+
+int main(int argc, char **argv) {
+  InitLLVM X(argc, argv);
+
+  cl::ParseCommandLineOptions(argc, argv);
+
+  const char *DebuginfodUrlsEnv = std::getenv("DEBUGINFOD_URLS");
+  if (DebuginfodUrlsEnv == NULL) {
+    errs() << "DEBUGINFOD_URLS not set\n";
+    return 1;
+  }
+
+  SmallVector<StringRef> DebuginfodUrls;
+  StringRef(DebuginfodUrlsEnv).split(DebuginfodUrls, " ");
+
+  const char *HomeEnv = std::getenv("HOME");
+  if (HomeEnv == NULL) {
+    LLVM_DEBUG(dbgs() << "HOME not set\n";);
+    return 1;
+  }
+  LLVM_DEBUG(dbgs() << "HOME = " << HomeEnv << "\n";);
+  auto CacheDirectoryPath =
+      std::string(HomeEnv) +
+      std::string("/.llvmdebuginfodcache/debuginfod_client");
+  LLVM_DEBUG(dbgs() << "CacheDirectoryPath = " << CacheDirectoryPath << "\n";);
+
+  DebuginfodAssetType Type;
+  StringRef Description;
+  if (FetchExecutable) {
+    Type = DebuginfodAssetType::Executable;
+  } else if (FetchDebuginfo) {
+    Type = DebuginfodAssetType::Debuginfo;
+  } else if (FetchSource != "") {
+    Type = DebuginfodAssetType::Source;
+    Description = FetchSource;
+  } else {
+    llvm_unreachable("invalid asset request");
+  }
+  std::string InfoFilePath = ExitOnErr(fetchInfo(
+      DebuginfodUrls, CacheDirectoryPath, InputBuildID, Type, Description));
+  outs() << InfoFilePath << "\n";
+}
+
+#undef DEBUG_TYPE

llvm/unittests/Debuginfod/CMakeLists.txt

+set(LLVM_LINK_COMPONENTS
+  Debuginfod
+  )
+
+add_llvm_unittest(DebuginfodTests
+  DebuginfodTests.cpp
+  )

llvm/unittests/Debuginfod/DebuginfodTests.cpp

+//===-- llvm/unittest/Support/DebuginfodTests.cpp - unit tests --*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifdef LLVM_ENABLE_DEBUGINFOD_CLIENT
+
+#include "llvm/Debuginfod/Debuginfod.h"
+
+#include "gtest/gtest.h"
+
+TEST(DebuginfodTests, noDebuginfodUrlsFetchInfoTest) {
+  auto InfoOrErr = fetchInfo({}, "./", "fakeBuildId",
+                             llvm::DebuginfodAssetType::Executable, "");
+  handleAllErrors(InfoOrErr.takeError(), [](const llvm::StringError &SE) {
+    llvm::dbgs() << "got a StringError as expected\n";
+  });
+}
+
+#endif

llvm/unittests/Support/CMakeLists.txt

add_llvm_unittest(SupportTests
   FileCollectorTest.cpp
   FileOutputBufferTest.cpp
   FileUtilitiesTest.cpp
   FormatVariadicTest.cpp
   FSUniqueIDTest.cpp
   GlobPatternTest.cpp
   HashBuilderTest.cpp
   Host.cpp
+  HTTPClient.cpp
   IndexedAccessorTest.cpp
   InstructionCostTest.cpp
   ItaniumManglingCanonicalizerTest.cpp
   JSONTest.cpp
   KnownBitsTest.cpp
   LEB128Test.cpp
   LinearPolyBaseTest.cpp
   LineIteratorTest.cpp

llvm/unittests/Support/HTTPClient.cpp

+//===-- llvm/unittest/Support/HTTPClient.cpp - unit tests -------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifdef LLVM_WITH_CURL
+
+#include "llvm/Support/HTTPClient.h"
+
+#include "gtest/gtest.h"
+
+TEST(HTTPClientTests, invalidUrlTest) {
+  std::string invalidUrl = "llvm is fun";
+  handleAllErrors(llvm::httpGet(invalidUrl).takeError(),
+                  [](const llvm::StringError &SE) {
+                    llvm::dbgs() << "got a StringError as expected\n";
+                  });
+}
+
+#endif