Implement bmalloc::isASanEnabled for generic Unix

[Michael Catanzaro]

If you only care about Clang (not sure), bmalloc::isASanEnabled could be as simple as:

static bool isASanEnabled()
{
#if defined(__has_feature) && __has_feature(address_sanitizer)
    return true;
#else
    return false;
#endif
}

Unless there is some reason I don't understand for the runtime check.

GCC supports asan but not __has_feature. This runtime check works:

    void *handle = dlopen(nullptr, RTLD_NOW);
    if (!handle)
        return false;
    bool result = !!dlsym(handle, "__asan_poison_memory_region");
    dlclose(handle);
    return result;

I expect that would work fine on Darwin too.

[Michael Catanzaro]

Created attachment 260254 [details]
Patch

[Michael Catanzaro]

Created attachment 260255 [details]
Patch

[Alexey Proskuryakov]

The runtime check is needed because we need to disable bmalloc whenever ASan is enabled in the process - even if bmalloc itself is compiled without ASan.

[Michael Catanzaro]

OK, that makes sense.

[Michael Catanzaro]

Created attachment 260289 [details]
Patch

[Geoffrey Garen]

Comment on attachment 260289 [details]
Patch

r=me

[Michael Catanzaro]

Committed r189181: <http://trac.webkit.org/changeset/189181>