Build LLVM / Clang on MacOS

README.md

Build LLVM / Clang on MacOS

Problem

Built-in Clang / LLVM shipped by Xcode does not support Leak Santizer (-fsantize=leak) feature. For example, this code has memory leak:

// File: main.c

#include <stdlib.h>

int main() {
	int *array = (int *)malloc(sizeof(int) * 100);
	array = NULL;   // <--- Memory Leak
	return 0;
}

• Compile with clang will throws an exception:

$ which clang
/usr/bin/clang

$ clang -g -fsanitize=leak main.c   
clang: error: unsupported option '-fsanitize=leak' for target 'x86_64-apple-darwin18.2.0'

The Fix:

• Install latest Clang/LLVM with Homebrew

brew install llvm@8

• Overwrite the default Clang with latest Clang

echo 'export PATH="/usr/local/opt/llvm/bin:$PATH"'

• Make sure Clang is updated

$ which clang
/usr/local/opt/llvm/bin/clang

Result:

clang -g -fsanitize=leak main.c

$ ./a.out

=================================================================
==2895==ERROR: LeakSanitizer: detected memory leaks

Direct leak of 400 byte(s) in 1 object(s) allocated from:
    #0 0x107922de6 in wrap_malloc (libclang_rt.lsan_osx_dynamic.dylib:x86_64h+0x7de6)
    #1 0x107914f78 in main main.c:4   # <----- It points out the potential cause of memory leak!! :D
    #2 0x7fff7cbdced8 in start (libdyld.dylib:x86_64+0x16ed8)

SUMMARY: LeakSanitizer: 400 byte(s) leaked in 1 allocation(s).

Be sure to use the following instead on newer macOS (i.e. ARM macOS):

echo 'export PATH="/opt/homebrew/opt/llvm/bin:$PATH"' >> ~/.zshrc