[GWP-ASan] Build stack_trace_compressor_fuzzer.

[hctim]

Summary

Flips the switch to build stack_trace_compressor_fuzzer. This was recently
temporarily disabled in rL369079 as it was breaking the sanitizer buildbots.

My diagnosis of the problem is that on clang-only bootstrap builds, we build
gwp_asan before libfuzzer. This causes a discrepancy when the clang driver
attempts to link libclang_rt.fuzzer* as CMake doesn't see a dependency there.

I've (hopefully) fixed the issue by adding a direct dependency for the fuzz
target so CMake can resolve the build order properly. As part of this, the
libFuzzer 'fuzzer' target has to be discovered before the declaration of the
fuzz target.

pcc@ for mild review + notification as buildcop.

[pcc]

compiler-rt/lib/gwp_asan/CMakeLists.txt

115–116 ↗

(On Diff #216232)

Shouldn't the order of these be reversed, i.e.

add_dependencies(stack_trace_compressor_fuzzer gwp_asan fuzzer)

https://cmake.org/cmake/help/latest/command/add_dependencies.html

I think that means that you don't need to move the target ordering around.

[hctim]

compiler-rt/lib/gwp_asan/CMakeLists.txt

115–116 ↗

(On Diff #216232)

Thanks for the catch - looks like this resolves the issue. Slight change is that the desire is for the fuzzer to be built with ninja gwp_asan, so the add_dependencies(gwp_asan stack_trace_compressor_fuzzer) is WAI :)

[hctim]

• Reverse order of fuzzer dependencies.

[pcc]

compiler-rt/lib/gwp_asan/CMakeLists.txt

115–116 ↗

(On Diff #216232)

That dependency edge seems mildly surprising to me, but it's your project.

That aside though, how is this linking successfully without a dependency from the fuzzer to gwp_asan?

[pcc]

LGTM

compiler-rt/lib/gwp_asan/CMakeLists.txt

115–116 ↗

(On Diff #216232)

Oh, I see the ${GWP_ASAN_SOURCES} now. Never mind.

[phosek]

This seems to have broke our toolchain build, specifically the stage that (cross-)compiles runtimes for i386-linux-gnu:

[697/697] Linking CXX executable compiler-rt/lib/gwp_asan/stack_trace_compressor_fuzzer
FAILED: compiler-rt/lib/gwp_asan/stack_trace_compressor_fuzzer 
: && /b/s/w/ir/k/recipe_cleanup/clangB3DKrD/llvm_build_dir/./bin/clang++ --target=i386-unknown-linux-gnu --sysroot=/b/s/w/ir/k/cipd/linux-i386  -resource-dir=/b/s/w/ir/k/recipe_cleanup/clangB3DKrD/llvm_build_dir/tools/clang/stage2-bins/./lib/clang/10.0.0 -fPIC -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -std=c++14 -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wstring-conversion -fdiagnostics-color -ffunction-sections -fdata-sections -fdebug-prefix-map=/b/s/w/ir/k/recipe_cleanup/clangB3DKrD/llvm_build_dir/tools/clang/stage2-bins/runtimes/runtimes-i386-unknown-linux-gnu-bins=../recipe_cleanup/clangB3DKrD/llvm_build_dir/tools/clang/stage2-bins/runtimes/runtimes-i386-unknown-linux-gnu-bins -fdebug-prefix-map=/b/s/w/ir/k/llvm-project/= -no-canonical-prefixes -Wall -std=c++14 -Wno-unused-parameter -O2 -g -DNDEBUG  -resource-dir=/b/s/w/ir/k/recipe_cleanup/clangB3DKrD/llvm_build_dir/tools/clang/stage2-bins/./lib/clang/10.0.0 -fuse-ld=lld -fuse-ld=lld -Wl,--color-diagnostics   -fsanitize=fuzzer compiler-rt/lib/gwp_asan/CMakeFiles/stack_trace_compressor_fuzzer.dir/stack_trace_compressor_fuzzer.cpp.o compiler-rt/lib/gwp_asan/CMakeFiles/stack_trace_compressor_fuzzer.dir/platform_specific/guarded_pool_allocator_posix.cpp.o compiler-rt/lib/gwp_asan/CMakeFiles/stack_trace_compressor_fuzzer.dir/platform_specific/mutex_posix.cpp.o compiler-rt/lib/gwp_asan/CMakeFiles/stack_trace_compressor_fuzzer.dir/guarded_pool_allocator.cpp.o compiler-rt/lib/gwp_asan/CMakeFiles/stack_trace_compressor_fuzzer.dir/random.cpp.o compiler-rt/lib/gwp_asan/CMakeFiles/stack_trace_compressor_fuzzer.dir/stack_trace_compressor.cpp.o  -o compiler-rt/lib/gwp_asan/stack_trace_compressor_fuzzer   && :
ld.lld: error: unable to find library -lc++
ld.lld: error: unable to find library -lc++
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
ninja: build stopped: subcommand failed.
FAILED: runtimes/runtimes-i386-unknown-linux-gnu-stamps/runtimes-i386-unknown-linux-gnu-build

Is this supposed to be linking libc++?

[vitalybuka]

compiler-rt/trunk/lib/gwp_asan/CMakeLists.txt

104

We should not build these fuzzers if host compiler has no libFuzzer.

[vitalybuka]

compiler-rt/trunk/lib/gwp_asan/CMakeLists.txt

104

maybe do the same as clang/tools/clang-format/CMakeLists.txt

if( LLVM_LIB_FUZZING_ENGINE OR LLVM_USE_SANITIZE_COVERAGE )

[hctim]

@vitalybuka: Maybe rL369823?

[lebedev.ri]

I think this breaks compiler-rt build if the host compiler does not have compiler-rt present, cc @pree-jackie

[pree-jackie]

@hctim This breaks the debug build of llvm when the host compiler doesn't build with compiler-rt. I build llvm/clang (release build) as a host compiler, to build llvm,compiler-rt (debug) build. Unfortunately, while building the debug build, the process tries to find the already installed compiler-rt of the host compiler (which is not present). Do you have any guidelines?

You can also check the build process error log : https://pastebin.com/Q76H9FW9

Thanks

[hctim]

@pree-jackie i'll take a look, thanks for letting me know

[hctim]

Update: there's a slight problem with the dependency chain that I encountered when whipping up a quick fix:

stack_trace_compressor_fuzzer requires:

• libFuzzer
• asan/ubsan/msan (to be useful)

libFuzzer needs COMPILER_RT_HAS_SANITIZER_COMMON=True
COMPILER_RT_HAS_SANITIZER_COMMON needs LLVM_USE_SANITIZER=False

... so basically the fuzz target requires sanitization, but providing sanitization would cancel the build of the parent gwp_asan target...

Let me have a think. If I can't hack together a solution soon I'll just comment out the target to unbreak you.

compiler-rt/trunk/lib/gwp_asan/CMakeLists.txt

add_compiler_rt_object_libraries(RTGwpAsanBacktraceLibc
       CFLAGS ${GWP_ASAN_CFLAGS})
   add_compiler_rt_object_libraries(RTGwpAsanBacktraceSanitizerCommon
       ARCHS ${GWP_ASAN_SUPPORTED_ARCH}
       SOURCES optional/backtrace_sanitizer_common.cpp
       ADDITIONAL_HEADERS ${GWP_ASAN_BACKTRACE_HEADERS}
       CFLAGS ${GWP_ASAN_CFLAGS} ${SANITIZER_COMMON_CFLAGS})
 
   # Build the stack trace compressor fuzzer.
-  # Currently commented out in order to give me some time to figure out what the
-  # issue is. Rolling back would require rolling back 5 CL's, so this should be
-  # okay until I can get to a real computer and actually fix it tomorrow.
-  # - hctim
-  #if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang")
-  #  add_executable(stack_trace_compressor_fuzzer
-  #    stack_trace_compressor_fuzzer.cpp
-  #    ${GWP_ASAN_SOURCES}
-  #    ${GWP_ASAN_HEADERS})
-  #  set_target_properties(stack_trace_compressor_fuzzer
-  #    PROPERTIES FOLDER "Fuzzers")
-  #  target_compile_options(stack_trace_compressor_fuzzer
-  #    PRIVATE -fsanitize=fuzzer-no-link)
-  #  set_target_properties(
-  #    stack_trace_compressor_fuzzer PROPERTIES LINK_FLAGS -fsanitize=fuzzer)
-  #  add_dependencies(gwp_asan stack_trace_compressor_fuzzer)
-  #endif()
+  if ("${CMAKE_CXX_COMPILER_ID}" STREQUAL "Clang" AND
+      COMPILER_RT_BUILD_LIBFUZZER)
+    add_executable(stack_trace_compressor_fuzzer
+        stack_trace_compressor_fuzzer.cpp
+        ${GWP_ASAN_SOURCES}
+        ${GWP_ASAN_HEADERS})
+    set_target_properties(
+        stack_trace_compressor_fuzzer PROPERTIES FOLDER "Fuzzers")
+    target_compile_options(
+        stack_trace_compressor_fuzzer PRIVATE -fsanitize=fuzzer-no-link)
+    set_target_properties(
+        stack_trace_compressor_fuzzer PROPERTIES LINK_FLAGS -fsanitize=fuzzer)
+    add_dependencies(stack_trace_compressor_fuzzer fuzzer)
+    add_dependencies(gwp_asan stack_trace_compressor_fuzzer)
+  endif()
 endif()
 
 if(COMPILER_RT_INCLUDE_TESTS)
   add_subdirectory(tests)
 endif()