AIX: Work around for malloc(0) behavior

malloc(0) returning 0 is expected behavior on AIX but
compiling with -D_LINUX_SOURCE_COMPAT, malloc(0) should
return a valid pointer (which we do define for AIX). However,
including cstdlib resets the behaviour of _LINUX_SOURCE_COMPAT.
GCC bug: 79839

R=jochen@chromium.org, titzer@chromium.org
BUG=
LOG=N

Review-Url: https://codereview.chromium.org/2732743002
Cr-Commit-Position: refs/heads/master@{#43647}

src/d8.cc

@@ -100,7 +100,13 @@ class ShellArrayBufferAllocator : public v8::ArrayBuffer::Allocator {
 #if USE_VM
     if (RoundToPageSize(&length)) return VirtualMemoryAllocate(length);
 #endif
+// Work around for GCC bug on AIX
+// See: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79839
+#if V8_OS_AIX && _LINUX_SOURCE_COMPAT
+    return __linux_malloc(length);
+#else
     return malloc(length);
+#endif
   }
   virtual void Free(void* data, size_t length) {
 #if USE_VM

test/cctest/wasm/wasm-run-utils.h

@@ -110,7 +110,7 @@ class TestingModule : public ModuleEnv {
     CHECK_EQ(0, instance->mem_size);
     module_.has_memory = true;
     instance->mem_start = reinterpret_cast<byte*>(malloc(size));
-    CHECK(instance->mem_start);
+    CHECK(size == 0 || instance->mem_start);
     memset(instance->mem_start, 0, size);
     instance->mem_size = size;
     return raw_mem_start<byte>();