[llvm] [Debuginfod] Add cpp-httplib optional dependency.

[noajshu]

Summary

Adds optional dependency on cpp-httplib, a lightweight header-only HTTP server.

[noajshu]

Clean up old cmake comments.

[noajshu]

Add #cmakedefine for LLVM_ENABLE_CPP_HTTPLIB

[phosek]

llvm/CMakeLists.txt

418

I'd probably just call it LLVM_ENABLE_HTTPLIB, you already use HTTPLIB elsewhere (for example HAVE_HTTPLIB_HEADER).

llvm/cmake/config-ix.cmake

195–197

Why do we need to check all three?

[noajshu]

Change LLVM_ENABLE_CPP_HTTPLIB -> LLVM_ENABLE_HTTPLIB and remove redundant use of check_cxx_symbol_exists.

[noajshu]

llvm/cmake/config-ix.cmake

195–197

Good point, the additional checks are redundant. I've removed them.

[phosek]

LGTM

[noajshu]

Set default of LLVM_ENABLE_HTTPLIB to OFF

[noajshu]

Add back missing include(CheckCXXSymbolExists)

[noajshu]

Rebase against main.

[noajshu]

Re-run pre-merge checks

[noajshu]

Rebase against main

[noajshu]

Fix whitespace error

[noajshu]

Rebase against main

[noajshu]

Add back in accidentally deleted httplib package lookup in config-ix.cmake

[MaskRay]

Notes for next time.

The commit message (summary) should mention that you added LLVM_ENABLE_HTTPLIB.
It is an important build system detail and is convenient for archaeology when someone tries to find which commit introduced LLVM_ENABLE_HTTPLIB.

llvm/CMakeLists.txt

 else()
   option(LLVM_ENABLE_THREADS "Use threads if available." ON)
 endif()
 
 set(LLVM_ENABLE_ZLIB "ON" CACHE STRING "Use zlib for compression/decompression if available. Can be ON, OFF, or FORCE_ON")
 
 set(LLVM_ENABLE_CURL "OFF" CACHE STRING "Use libcurl for the HTTP client if available. Can be ON, OFF, or FORCE_ON")
 
+set(LLVM_ENABLE_HTTPLIB "OFF" CACHE STRING "Use cpp-httplib HTTP server library if available. Can be ON, OFF, or FORCE_ON")
+
 set(LLVM_Z3_INSTALL_DIR "" CACHE STRING "Install directory of the Z3 solver.")
 
 option(LLVM_ENABLE_Z3_SOLVER
   "Enable Support for the Z3 constraint solver in LLVM."
   ${LLVM_ENABLE_Z3_SOLVER_DEFAULT}
 )
 
 if (LLVM_ENABLE_Z3_SOLVER)

llvm/cmake/config-ix.cmake

 if( WIN32 AND NOT CYGWIN )
   # We consider Cygwin as another Unix
   set(PURE_WINDOWS 1)
 endif()
 
 include(CheckIncludeFile)
 include(CheckLibraryExists)
 include(CheckSymbolExists)
+include(CheckCXXSymbolExists)
 include(CheckFunctionExists)
 include(CheckStructHasMember)
 include(CheckCCompilerFlag)
 include(CMakePushCheckState)
 
 include(CheckCompilerVersion)
 include(HandleLLVMStdlib)
 
if(CURL_FOUND)
     cmake_pop_check_state()
     if(LLVM_ENABLE_CURL STREQUAL FORCE_ON AND NOT HAVE_CURL)
       message(FATAL_ERROR "Failed to configure curl")
     endif()
   endif()
   set(LLVM_ENABLE_CURL "${HAVE_CURL}")
 endif()
 
+if(LLVM_ENABLE_HTTPLIB)
+  if(LLVM_ENABLE_HTTPLIB STREQUAL FORCE_ON)
+    find_package(httplib REQUIRED)
+  else()
+    find_package(httplib)
+  endif()
+  if(HTTPLIB_FOUND)
+    # Check if the "httplib" we found is usable; for example there may be another
+    # library with the same name.
+    cmake_push_check_state()
+    list(APPEND CMAKE_REQUIRED_LIBRARIES ${HTTPLIB_LIBRARY})
+    check_cxx_symbol_exists(CPPHTTPLIB_HTTPLIB_H ${HTTPLIB_HEADER_PATH} HAVE_HTTPLIB)
+    cmake_pop_check_state()
+    if(LLVM_ENABLE_HTTPLIB STREQUAL FORCE_ON AND NOT HAVE_HTTPLIB)
+      message(FATAL_ERROR "Failed to configure cpp-httplib")
+    endif()
+  endif()
+  set(LLVM_ENABLE_HTTPLIB "${HAVE_HTTPLIB}")
+endif()
+
 # Don't look for these libraries if we're using MSan, since uninstrumented third
 # party code may call MSan interceptors like strlen, leading to false positives.
 if(NOT LLVM_USE_SANITIZER MATCHES "Memory.*")
   # Don't look for these libraries on Windows.
   if (NOT PURE_WINDOWS)
     # Skip libedit if using ASan as it contains memory leaks.
     if (LLVM_ENABLE_LIBEDIT AND HAVE_HISTEDIT_H AND NOT LLVM_USE_SANITIZER MATCHES ".*Address.*")
       check_library_exists(edit el_init "" HAVE_LIBEDIT)

llvm/include/llvm/Config/llvm-config.h.cmake

 #cmakedefine01 LLVM_FORCE_ENABLE_STATS
 
 /* Define if we have z3 and want to build it */
 #cmakedefine LLVM_WITH_Z3 ${LLVM_WITH_Z3}
 
 /* Define if we have curl and want to use it */
 #cmakedefine LLVM_ENABLE_CURL ${LLVM_ENABLE_CURL}
 
+/* Define if we have cpp-httplib and want to use it */
+#cmakedefine LLVM_ENABLE_HTTPLIB ${LLVM_ENABLE_HTTPLIB}
+
 /* Define if LLVM was built with a dependency to the libtensorflow dynamic library */
 #cmakedefine LLVM_HAVE_TF_API
 
 /* Define to 1 if you have the <sysexits.h> header file. */
 #cmakedefine HAVE_SYSEXITS_H ${HAVE_SYSEXITS_H}
 
 /* Define to 1 to enable the experimental new pass manager by default */
 #cmakedefine01 LLVM_ENABLE_NEW_PASS_MANAGER