[compiler-rt] Fix build of Sanitizer-${arch}-Test-Nolibc

[smeenai]

Summary

After https://reviews.llvm.org/D146920 fixed the compiler check for it,
we're adding -ftrivial-auto-var-init=pattern to SANITIZER_COMMON_CFLAGS,
which can result in calls to memset. However, RTSanitizerCommon and
RTSanitizerCommonNoLibc are supposed to be independent of libc, which is
tested by Sanitizer-${arch}-Test-Nolibc, and that test was failing to
link as a result. Build these two libraries without auto var init to
avoid the libc dependency.

[barannikov88]

There seem to be an issue with tsan?

[smeenai]

The test failure is occurring on the base revision as well, so it's not caused by my change.

[phosek]

compiler-rt/lib/sanitizer_common/CMakeLists.txt

223–224

Could we alternatively add -ftrivial-auto-var-init=unititilized to override -ftrivial-auto-var-init=pattern that was added earlier?

[vitalybuka]

compiler-rt/lib/sanitizer_common/CMakeLists.txt

223–224

I commented about that D135716, but didn't insist as to my surprise we see no symptoms. I didn't realize it's just quotes.

Only tsan has a test for that, other sanitizers will have the same issue.

I think safer to limit this flag to platforms without interceptors, like FUCSHIA, and find solution for general case later, like inserting special path to replace memsets with internal_memsets.

[vitalybuka]

Is this still needed?

[smeenai]

It'll be needed if D146920 relands. CC @barannikov88

[barannikov88]

In D147164#4622115, @smeenai wrote:

It'll be needed if D146920 relands. CC @barannikov88

There is an issue I unfortunately don't have time to figure out how to solve: check_cxx_compiler_flag uses CMAKE_CXX_FLAGS, which contains -Wall (implies -Wformat), but CMAKE_CXX_FLAGS is not used when building builtins (they are built as "custom targets").
As a result, when using gcc, check_cxx_compiler_flag("-Wformat-security -Werror" ...) passes, but the compilation fails because gcc doesn't like -Wformat-security without -Wformat.
I think CMAKE_CXX_FLAGS contains -Wall because of inclusion of AddLLVM.cmake somewhere in the runtimes.

compiler-rt/lib/sanitizer_common/CMakeLists.txt

 
 append_rtti_flag(OFF SANITIZER_CFLAGS)
 
 append_list_if(SANITIZER_LIMIT_FRAME_SIZE -Wframe-larger-than=570
                SANITIZER_CFLAGS)
 append_list_if(COMPILER_RT_HAS_WGLOBAL_CONSTRUCTORS_FLAG -Wglobal-constructors
                SANITIZER_CFLAGS)
 
+set(LIBC_INDEPENDENT_SANITIZER_CFLAGS ${SANITIZER_CFLAGS})
+# This may call memset, which we wish to avoid for the libc-independent libraries
+list(FILTER LIBC_INDEPENDENT_SANITIZER_CFLAGS EXCLUDE REGEX ^-ftrivial-auto-var-init=)
+
 if(APPLE)
   set(OS_OPTION OS ${SANITIZER_COMMON_SUPPORTED_OS})
 endif()
 
 add_compiler_rt_object_libraries(RTSanitizerCommon
   ${OS_OPTION}
   ARCHS ${SANITIZER_COMMON_SUPPORTED_ARCH}
   SOURCES ${SANITIZER_SOURCES}
   ADDITIONAL_HEADERS ${SANITIZER_IMPL_HEADERS}
-  CFLAGS ${SANITIZER_CFLAGS}
+  CFLAGS ${LIBC_INDEPENDENT_SANITIZER_CFLAGS}
   DEFS ${SANITIZER_COMMON_DEFINITIONS})
 add_compiler_rt_object_libraries(RTSanitizerCommonNoTermination
   ${OS_OPTION}
   ARCHS ${SANITIZER_COMMON_SUPPORTED_ARCH}
   SOURCES ${SANITIZER_SOURCES_NOTERMINATION}
   ADDITIONAL_HEADERS ${SANITIZER_IMPL_HEADERS}
   CFLAGS ${SANITIZER_CFLAGS}
   DEFS ${SANITIZER_COMMON_DEFINITIONS})
 add_compiler_rt_object_libraries(RTSanitizerCommonNoLibc
   ${OS_OPTION}
   ARCHS ${SANITIZER_COMMON_SUPPORTED_ARCH}
   SOURCES ${SANITIZER_NOLIBC_SOURCES}
   ADDITIONAL_HEADERS ${SANITIZER_IMPL_HEADERS}
-  CFLAGS ${SANITIZER_CFLAGS}
+  CFLAGS ${LIBC_INDEPENDENT_SANITIZER_CFLAGS}
   DEFS ${SANITIZER_COMMON_DEFINITIONS})
 add_compiler_rt_object_libraries(RTSanitizerCommonLibc
   ${OS_OPTION}
   ARCHS ${SANITIZER_COMMON_SUPPORTED_ARCH}
   SOURCES ${SANITIZER_LIBCDEP_SOURCES}
   ADDITIONAL_HEADERS ${SANITIZER_IMPL_HEADERS}
   CFLAGS ${SANITIZER_CFLAGS}
   DEFS ${SANITIZER_COMMON_DEFINITIONS})