606270 - xpcjsruntime.cpp:1072: warning: ignoring return value of 'int moz_posix_memalign(void**, size_t, size_t)', declared with attribute warn_unused_result

Status: RESOLVED FIXED

(Core :: XPConnect, defect)

Description

[Daniel Holbert [:dholbert]]

js/src/xpconnect/src/xpcjsruntime.cpp: In member function 'virtual void* XPConnectGCChunkAllocator::doAlloc()':
js/src/xpconnect/src/xpcjsruntime.cpp:1072: warning: ignoring return value of 'int moz_posix_memalign(void**, size_t, size_t)', declared with attribute warn_unused_result

References:
http://mxr.mozilla.org/mozilla-central/source/js/src/xpconnect/src/xpcjsruntime.cpp#1072
http://mxr.mozilla.org/mozilla-central/source/memory/mozalloc/mozalloc.h#149

The code in question is:
1069     virtual void *doAlloc() {
1070         void *chunk = 0;
1071 #ifdef MOZ_MEMORY
1072         posix_memalign(&chunk, js::GC_CHUNK_SIZE, js::GC_CHUNK_SIZE);
1073 #else
1074         chunk = js::AllocGCChunk();
1075 #endif
1076         if (chunk)
1077             mNumGCChunksInUse++;
1078         return chunk;
1079     }

(note that posix_memalign is #defined to moz_posix_memalign in my configuration)

So posix_memalign returns an error code on failure.  The flagged code assumes that it'll *also* leave |chunk| unmodified (or null it out) on failure.  However, the man page for posix_memalign doesn't make that guarantee:
http://www.opengroup.org/onlinepubs/000095399/functions/posix_memalign.html

So, I think we should be checking the return value here. (particularly since the function's declaration asks us to)

Comment 1

[Daniel Holbert [:dholbert]]

Attachment: fix

Comment 2

[Daniel Holbert [:dholbert]]

Comment on attachment 485086 [details] [diff] [review]
fix

Requesting approval to land on mozilla-central.

This is a correctness fix to fix a build warning; no anticipated functional change.

Comment 3

[Daniel Holbert [:dholbert]]

Landed:
http://hg.mozilla.org/mozilla-central/rev/8f7caade3cf0