[compiler-rt] Exclude compiler-rt from using -fmodules when LLVM_ENABLE_MODULES=On

[kubamracek]

Summary

Sanitizers are intentionally not including system headers and often declare slightly different function prototypes, which is incompatible with -fmodules and -fcxx-modules. Let’s simply exclude compiler-rt from using -fmodules.

[aprantl]

Thanks! This will allow us to enable compiler-rt on the http://lab.llvm.org:8080/green/job/clang-stage2-cmake-modulesRDA/ bot again.

For more context; on Darwin building compiler-rt with modules enabled produces errors like:

../projects/compiler-rt/lib/asan/../sanitizer_common/sanitizer_common_interceptors.inc:784:22: error: conflicting types for 'pread'
INTERCEPTOR(SSIZE_T, pread, int fd, void *ptr, SIZE_T count, OFF_T offset) {
^
<...>/usr/include/unistd.h:576:10: note: previous declaration is here
ssize_t pread(int __fd, void * __buf, size_t __nbyte, off_t __offset) __DARWIN_ALIAS_C(pread);
^
In file included from ../projects/compiler-rt/lib/asan/asan_interceptors.cc:205:
../projects/compiler-rt/lib/asan/../sanitizer_common/sanitizer_common_interceptors.inc:784:22: error: declaration of 'pread' must be imported from module 'Darwin.POSIX.unistd' before it is required
INTERCEPTOR(SSIZE_T, pread, int fd, void *ptr, SIZE_T count, OFF_T offset) {
^

[kubamracek]

r283658

compiler-rt/trunk/CMakeLists.txt

elseif(MSVC)
   # warning from the MS linker complaining that it can't find the 'vc140.pdb'
   # file used by our object library compilations.
   list(APPEND SANITIZER_COMMON_CFLAGS /Z7)
   llvm_replace_compiler_option(CMAKE_CXX_FLAGS "/Z[i7I]" "/Z7")
   llvm_replace_compiler_option(CMAKE_CXX_FLAGS_DEBUG "/Z[i7I]" "/Z7")
   llvm_replace_compiler_option(CMAKE_CXX_FLAGS_RELWITHDEBINFO "/Z[i7I]" "/Z7")
 endif()
 
+if(LLVM_ENABLE_MODULES)
+  # Sanitizers cannot be built with -fmodules. The interceptors intentionally
+  # don't include system headers, which is incompatible with modules.
+  list(APPEND SANITIZER_COMMON_CFLAGS -fno-modules)
+endif()
+
 # Turn off several warnings.
 append_list_if(COMPILER_RT_HAS_WGNU_FLAG -Wno-gnu SANITIZER_COMMON_CFLAGS)
 append_list_if(COMPILER_RT_HAS_WVARIADIC_MACROS_FLAG -Wno-variadic-macros SANITIZER_COMMON_CFLAGS)
 append_list_if(COMPILER_RT_HAS_WC99_EXTENSIONS_FLAG -Wno-c99-extensions SANITIZER_COMMON_CFLAGS)
 append_list_if(COMPILER_RT_HAS_WNON_VIRTUAL_DTOR_FLAG -Wno-non-virtual-dtor SANITIZER_COMMON_CFLAGS)
 append_list_if(COMPILER_RT_HAS_WD4146_FLAG /wd4146 SANITIZER_COMMON_CFLAGS)
 append_list_if(COMPILER_RT_HAS_WD4291_FLAG /wd4291 SANITIZER_COMMON_CFLAGS)
 append_list_if(COMPILER_RT_HAS_WD4391_FLAG /wd4391 SANITIZER_COMMON_CFLAGS)