[libFuzzer] [NFC] Make compiler command generation more readable.

[george.karpenkov]

Summary

Use config.clang as a more general option than config.c_compiler.

[morehouse]

test/fuzzer/lit.cfg

53

How is config.clang more general than config.c_compiler? What if the host doesn't have clang installed?

65

I think the original name makes more sense here. This is a list of the arguments to -fsanitize, not the full cmd.

[george.karpenkov]

test/fuzzer/lit.cfg

53

What if the host doesn't have clang installed?

Well then they don't get to run the LIT tests, which are tightly coupled with trunk version of Clang.
config.clang option adds a bunch of flags to config.c_compiler which might be required for a given build.

65

I guess it could be changed. The logic here was to have all names which go into the final compilation command be postfixed with _cmd

[morehouse]

test/fuzzer/lit.cfg

65

Sure, I think the final variable should be called sanitizers_cmd, but it does seem a bit confusing to change the type of sanitizers_cmd from a list to a string here.

[vitalybuka]

test/fuzzer/lit.cfg

59

same about

link_cmd = '-lc++' if any(x in config.target_triple for x in ('darwin', 'freebsd')) else '-lstdc++'

71

such renaming and reformatting should be in separate patches

also I like current oneliner: isysroot_cmd = config.osx_sysroot_flag if config.osx_sysroot_flag else ''

[george.karpenkov]

test/fuzzer/lit.cfg

71

It stops being one-liner in a subsequent revision.

[george.karpenkov]

test/fuzzer/lit.cfg

59

that's more complex though, it has nested if-s, and the current version explicitly enumerates four conditions

test/fuzzer/lit.cfg

 else:
   lit_config.note('linux feature unavailable')
 
 config.substitutions.append(('%build_dir', config.cmake_binary_dir))
 libfuzzer_src_root = os.path.join(config.compiler_rt_src_root, "lib", "fuzzer")
 config.substitutions.append(('%libfuzzer_src', libfuzzer_src_root))
 
 def generate_compiler_cmd(is_cpp=True, fuzzer_enabled=True):
-  compiler_cmd = config.c_compiler
+  compiler_cmd = config.clang
   if config.clang and config.stdlib == 'libc++':
     link_cmd = '-stdlib=libc++ -Wl,-rpath=%s' % config.llvm_library_dir
   elif config.clang and config.stdlib == 'static-libc++':
-    link_cmd = '-stdlib=libc++ -lc++abi -static-libstdc++ -Wl,-rpath=%s' % config.llvm_library_dir
+    link_cmd = '-stdlib=libc++ -lc++abi -static-libstdc++ -Wl,-rpath=%s' % (
+        config.llvm_library_dir)
+  elif any(x in config.target_triple for x in ('darwin', 'freebsd')):
+    link_cmd = '-lc++'
   else:
-    link_cmd = '-lc++' if any(x in config.target_triple for x in ('darwin', 'freebsd')) else '-lstdc++'
+    link_cmd = '-lstdc++'
+
   std_cmd = '--driver-mode=g++ -std=c++11' if is_cpp else ''
   sanitizers = ['address']
   if fuzzer_enabled:
     sanitizers.append('fuzzer')
   sanitizers_cmd = ('-fsanitize=%s' % ','.join(sanitizers))
-  isysroot_cmd = config.osx_sysroot_flag if config.osx_sysroot_flag else ''
-  include_cmd = '-I%s' % libfuzzer_src_root
-  return '%s %s %s -O2 -gline-tables-only %s %s %s' % (
-      compiler_cmd, std_cmd, link_cmd, isysroot_cmd, sanitizers_cmd, include_cmd)
+  if config.osx_sysroot_flag:
+    isysroot_cmd = config.osx_sysroot_flag
+  else:
+    isysroot_cmd = ''
+  return " ".join([
+    compiler_cmd,
+    std_cmd,
+    link_cmd,
+    "-O2 -gline-tables-only",
+    isysroot_cmd,
+    sanitizers_cmd,
+    "-I%s" % libfuzzer_src_root
+  ])
 
 config.substitutions.append(('%cpp_compiler',
       generate_compiler_cmd(is_cpp=True, fuzzer_enabled=True)
       ))
 
 config.substitutions.append(('%c_compiler',
       generate_compiler_cmd(is_cpp=False, fuzzer_enabled=True)
       ))
 
 config.substitutions.append(('%no_fuzzer_cpp_compiler',
       generate_compiler_cmd(is_cpp=True, fuzzer_enabled=False)
       ))
 
 config.substitutions.append(('%no_fuzzer_c_compiler',
       generate_compiler_cmd(is_cpp=False, fuzzer_enabled=False)
       ))