[libFuzzer] Fix lit files to make running tests more straightforward on Mac OS.

[Dor1s]

Summary

Current implementation does not work if CMAKE_OSX_SYSROOT is not specified.

It silently generates invalid command with the following flags:

-std=c++11 -lc++ -gline-tables-only -isysroot -fsanitize=address,fuzzer

and then fails with the following error:

warning: no such sysroot directory: '-fsanitize=address,fuzzer' [-Wmissing-sysroot]"
<...>/RepeatedBytesTest.cpp:5:10: fatal error: 'assert.h' file not found
#include <assert.h>
         ^~~~~~~~~~
1 error generated.

However, if you have Command Line Tools installed, you have '/usr/include' dir.
In that case, it is not necessary to specify isysroot path.

Also, with the patch, in case of '/usr/include' does not exist, the '-sysroot'
path would be resolved automatically in compiler-rt/cmake/base-config-ix.cmake.

For more context, see the comment at compiler-rt/cmake/base-config-ix.cmake#L76

[george.karpenkov]

LGTM assuming tests pass on OS X and Linux.
You're right, I did hit an error with an empty -isysroot on our buildbot before as well.

[george.karpenkov]

@Dor1s btw for full context instead of linking to the file you can just do git diff -U999.

[kcc]

LGTM

@Dor1s btw for full context instead of linking to the file you can just do git diff -U999.

Better just use 'arc'

[Dor1s]

Thanks for the review. I'll verify that tests on Linux are not broken and commit it tomorrow. On Mac OS tests are passing fine.

I'm using arc. Regarding the context, I meant "context" as an additional information about handling of existing and non-existing /usr/include. I understood that the link is confusing, will replace with compiler-rt/cmake/base-config-ix.cmake#L76.

[Dor1s]

Tests pass on Linux as well.

test/fuzzer/lit.cfg

 def generate_compiler_cmd(is_cpp=True, fuzzer_enabled=True):
   compiler_cmd = config.c_compiler
   link_cmd = '-lc++' if 'darwin' in config.target_triple else '-lstdc++'
   std_cmd = '-std=c++11' if is_cpp else ''
   sanitizers = ['address']
   if fuzzer_enabled:
     sanitizers.append('fuzzer')
   sanitizers_cmd = ('-fsanitize=%s' % ','.join(sanitizers))
-  isysroot_cmd = ('-isysroot %s' % config.osx_sysroot
-      ) if 'darwin' in config.target_triple else ''
+  isysroot_cmd = config.osx_sysroot_flag if config.osx_sysroot_flag else ''
   include_cmd = '-I%s' % libfuzzer_src_root
   return '%s %s %s -gline-tables-only %s %s %s' % (
       compiler_cmd, std_cmd, link_cmd, isysroot_cmd, sanitizers_cmd, include_cmd)
 
 config.substitutions.append(('%cpp_compiler',
       generate_compiler_cmd(is_cpp=True, fuzzer_enabled=True)
       ))
 

test/fuzzer/lit.site.cfg.in

 @LIT_SITE_CFG_IN_HEADER@
 
 config.test_exec_root = "@CMAKE_CURRENT_BINARY_DIR@"
 
 config.cpp_compiler = "@LIBFUZZER_TEST_COMPILER@"
 config.target_flags = "@LIBFUZZER_TEST_FLAGS@"
 config.c_compiler = "@LIBFUZZER_TEST_COMPILER@"
 
-config.osx_sysroot = "@CMAKE_OSX_SYSROOT@"
+config.osx_sysroot_flag = "@OSX_SYSROOT_FLAG@"
 config.cmake_binary_dir = "@CMAKE_BINARY_DIR@"
 config.target_triple = "@TARGET_TRIPLE@"
 
 # Load common config for all compiler-rt lit tests.
 lit_config.load_config(config,
     "@COMPILER_RT_BINARY_DIR@/test/lit.common.configured")
 
 lit_config.load_config(config, "@CMAKE_CURRENT_SOURCE_DIR@/lit.cfg")