[PATCH] D62622: [CMake] Provide an option to use relative paths in debug info

[Petr Hosek via Phabricator via cfe-commits]

phosek created this revision.
phosek added reviewers: beanz, smeenai.
Herald added subscribers: llvm-commits, cfe-commits, aprantl, mgorny.
Herald added projects: clang, LLVM.

CMake always uses absolute file paths in the generated compiler
invocation which results in absolute file paths being embedded in debug
info. This is undesirable when building a toolchain e.g. on bots as the
debug info may embed the bot source checkout path which is meaningless
anywhere else.

This change introduces the LLVM_USE_RELATIVE_PATHS which uses
-fdebug-prefix-map (where supported) options to rewrite paths embedded
into debug info with relative ones. Additionally, LLVM_SOURCE_PREFIX can
be used to override the path to source directory with a different one.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D62622

Files:
  clang/cmake/caches/Fuchsia-stage2.cmake
  llvm/cmake/modules/HandleLLVMOptions.cmake
  llvm/cmake/modules/LLVMExternalProjectUtils.cmake


Index: llvm/cmake/modules/LLVMExternalProjectUtils.cmake
===================================================================
--- llvm/cmake/modules/LLVMExternalProjectUtils.cmake
+++ llvm/cmake/modules/LLVMExternalProjectUtils.cmake
@@ -231,6 +231,8 @@
                -DLLVM_ENABLE_WERROR=${LLVM_ENABLE_WERROR}
                -DLLVM_HOST_TRIPLE=${LLVM_HOST_TRIPLE}
                -DLLVM_HAVE_LINK_VERSION_SCRIPT=${LLVM_HAVE_LINK_VERSION_SCRIPT}
+               -DLLVM_USE_RELATIVE_PATHS=${LLVM_USE_RELATIVE_PATHS}
+               -DLLVM_SOURCE_PREFIX=${LLVM_SOURCE_PREFIX}
                -DPACKAGE_VERSION=${PACKAGE_VERSION}
                -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
                -DCMAKE_MAKE_PROGRAM=${CMAKE_MAKE_PROGRAM}
Index: llvm/cmake/modules/HandleLLVMOptions.cmake
===================================================================
--- llvm/cmake/modules/HandleLLVMOptions.cmake
+++ llvm/cmake/modules/HandleLLVMOptions.cmake
@@ -977,3 +977,19 @@
     endif()
   endif()
 endif()
+
+option(LLVM_USE_RELATIVE_PATHS "Make builds independent of absolute file paths." OFF)
+set(LLVM_SOURCE_PREFIX "" CACHE STRING "LLVM source directory prefix")
+
+if(LLVM_USE_RELATIVE_PATHS)
+  check_c_compiler_flag("-fdebug-prefix-map=foo=bar" SUPPORTS_FDEBUG_PREFIX_MAP)
+  set(source_root "${CMAKE_CURRENT_SOURCE_DIR}/../..")
+  if(LLVM_ENABLE_PROJECTS_USED)
+    string(APPEND source_root "/..")
+  endif()
+  get_filename_component(source_root "${source_root}" ABSOLUTE)
+  file(RELATIVE_PATH relative_root "${source_root}" "${CMAKE_BINARY_DIR}")
+  append_if(SUPPORTS_FDEBUG_PREFIX_MAP "-fdebug-prefix-map=${CMAKE_BINARY_DIR}=${relative_root}" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+  append_if(SUPPORTS_FDEBUG_PREFIX_MAP "-fdebug-prefix-map=${source_root}/=${LLVM_SOURCE_PREFIX}" CMAKE_C_FLAGS CMAKE_CXX_FLAGS)
+  add_flag_if_supported("-no-canonical-prefixes" NO_CANONICAL_PREFIXES)
+endif()
Index: clang/cmake/caches/Fuchsia-stage2.cmake
===================================================================
--- clang/cmake/caches/Fuchsia-stage2.cmake
+++ clang/cmake/caches/Fuchsia-stage2.cmake
@@ -15,6 +15,7 @@
 set(LLVM_EXTERNALIZE_DEBUGINFO ON CACHE BOOL "")
 set(LLVM_INCLUDE_EXAMPLES OFF CACHE BOOL "")
 set(LLVM_INCLUDE_DOCS OFF CACHE BOOL "")
+set(LLVM_USE_RELATIVE_PATHS ON CACHE BOOL "")
 
 set(CLANG_DEFAULT_CXX_STDLIB libc++ CACHE STRING "")
 if(NOT APPLE)


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