[analyzer] Conditionnaly include clang Analysis examples with cmake.

[Jiboo]

Summary

Without this patch, the clang Analysis plugin examples (in clang/lib/Analysis/plugins) are always built and installed even if CLANG_BUILD_EXAMPLES is OFF.

When using llvm-toolchain-bionic in http://apt.llvm.org/bionic/ the package llvm-10-dev includes a LLVMExports.cmake which includes thus samples. See /data/user/lib/llvm-10/lib/cmake/llvm/LLVMExports.cmake in http://apt.llvm.org/bionic/pool/main/l/llvm-toolchain-snapshot/llvm-10-dev_10~svn372305-1~exp1%2b0~20190919071908.1206~1.gbp6f40e3_amd64.deb

When trying to use llvm-10-dev using CMake from travis (with this config https://github.com/Jiboo/wembed/blob/54e9664d615313f39e1a4325c1e7f028ce2b72db/.travis.yml), I get the error:

CMake Error at /usr/lib/llvm-10/lib/cmake/llvm/LLVMExports.cmake:1341 (message):
The imported target "SampleAnalyzerPlugin" references the file
   "/usr/lib/llvm-10/lib/SampleAnalyzerPlugin.so"
but this file does not exist.  Possible reasons include:
* The file was deleted, renamed, or moved to another location.
* An install or uninstall procedure did not complete successfully.
* The installation package was faulty and contained
   "/usr/lib/llvm-10/lib/cmake/llvm/LLVMExports.cmake"
but not all the files it references.

I couldn't find SampleAnalyzerPlugin.so in any other packages (clang-10-examples only has sources), so I tried to replicate the problem locally, CLANG_BUILD_EXAMPLES was OFF, although the sample plugins were built and installed. Deleting /usr/local/lib/SampleAnalyzerPlugin.so replicated the travis error.

This fix looks ok to me, although I'm no CMake expert, particularly in LLVM context, and I might cure a symptom and not the cause, but with this patch if CLANG_BUILD_EXAMPLES is OFF, they don't appear in LLVMExports.cmake are not build/installed, and vice-versa if it's ON.

[lebedev.ri]

Please upload all patches with full context (-U99999)

clang/lib/Analysis/plugins/CMakeLists.txt

1–2

Sure it isn't just the SampleAnalyzer that should be wrapped into CLANG_BUILD_EXAMPLES?

clang/test/CMakeLists.txt

130

Likewise

[Jiboo]

Updated to add -U999999.

[Jiboo]

clang/lib/Analysis/plugins/CMakeLists.txt

1–2

Dunno, I though they were all examples, due to their contents:

CheckerDependencyHandling: registry.addDependency("example.DependendentChecker", "example.Dependency");
CheckerOptionHandling: registry.addChecker(registerMyChecker, shouldRegisterMyChecker, "example.MyChecker", "Example Description",

[Szelethus]

Apologies for the intrusion, but these plugins were added by me, and test an important case for our internal plugins. Could you please give me just a day or so the check whether the tests work for us correctly?

[Jiboo]

@Szelethus take your time, I find it strange to be the first with the problem (couldn't find reference on google or llvm bug tracker), I wouldn't be surprised if I fucked up somewhere and that this patch isn't really necessary.

[lebedev.ri]

Actually, uh oh. @Jiboo can you please file this as a bug?
This really should go into next patch release. CC @tstellar

@Szelethus this breaks LLVMExports.cmake as compared with LLVM-8, so it's actually a critical bug.

[Jiboo]

Here you go: https://bugs.llvm.org/show_bug.cgi?id=43430

[Szelethus]

I have no objections to this patch. I know that a variety patches played with these plugins and it moved all over the place, so I see that these are kind of touchy :/

[aaronpuchert]

I didn't know about this patch and published D68172: adding BUILDTREE_ONLY still builds the examples, but doesn't install them. It's also used by other test plugins like llvm/lib/Transforms/Hello.
Thanks to @lebedev.ri for informing my about this patch.

[Jiboo]

@aaronpuchert thanks, that looks like a better fix than mine for PR43430, although I'm not sure D68172 obsoletes this patch.
@Szelethus could you confirm that thus examples shouldn't be built when CLANG_BUILD_EXAMPLES is OFF, and that this patch is still valid?

[aaronpuchert]

In D67877#1686961, @Jiboo wrote:

@Szelethus could you confirm that thus examples shouldn't be built when CLANG_BUILD_EXAMPLES is OFF, and that this patch is still valid?

The problem is that CLANG_BUILD_EXAMPLES is off by default. Maybe we want to build these plugins by default though to make sure there are no compiler errors. Since their compilation shouldn't take a lot of time, I think that is a reasonable position to assume.

[Jiboo]

Superseded by D68172.

clang/lib/Analysis/plugins/CMakeLists.txt

-if(CLANG_ENABLE_STATIC_ANALYZER AND LLVM_ENABLE_PLUGINS)
+if(CLANG_ENABLE_STATIC_ANALYZER AND LLVM_ENABLE_PLUGINS AND CLANG_BUILD_EXAMPLES)
   add_subdirectory(SampleAnalyzer)
   add_subdirectory(CheckerDependencyHandling)
   add_subdirectory(CheckerOptionHandling)

clang/test/CMakeLists.txt

   endif()
 endif()
 
-if (CLANG_ENABLE_STATIC_ANALYZER)
-  if (LLVM_ENABLE_PLUGINS)
-    list(APPEND CLANG_TEST_DEPS
-      SampleAnalyzerPlugin
-      CheckerDependencyHandlingAnalyzerPlugin
-      CheckerOptionHandlingAnalyzerPlugin
-      )
-  endif()
+if (CLANG_ENABLE_STATIC_ANALYZER AND CLANG_BUILD_EXAMPLES AND LLVM_ENABLE_PLUGINS)
+  list(APPEND CLANG_TEST_DEPS
+    SampleAnalyzerPlugin
+    CheckerDependencyHandlingAnalyzerPlugin
+    CheckerOptionHandlingAnalyzerPlugin
+    )
 endif()
 
 add_custom_target(clang-test-depends DEPENDS ${CLANG_TEST_DEPS})