Bug 12841 – Crash on ARM due to mis-alignment

• Component: New Bugs
• Status: RESOLVED FIXED

[Oscar Cwajbaum]

ARM has stricter alignment rules than many other architectures. In this case, pageheap_memory is being declared as a char array, so it is not aligned by the compiler. It is later used as TCMalloc_PageHeap*, which does require alignment.

When building under ARM, this patch tells the compiler to stricly align pageheap_memory so that pageheap_memory can be used as TCMalloc_PageHeap*. It does not affect other platforms.

[Oscar Cwajbaum]

Created attachment 13292 [details]
Fix ARM crash due to mis-alignment

[Darin Adler]

Comment on attachment 13292 [details]
Fix ARM crash due to mis-alignment

I think there's a more-portable way to solve this problem. We could make pageheap_memory be an array of pointers instead of an array of char. That would ive us the alignment we need to store pointers in it.

static void* pageheap_memory[(sizeof(TCMalloc_PageHeap) + sizeof(void*) - 1) / sizeof(void*)];

What do you think?

[Maciej Stachowiak]

I agree with Darin. I think it is better to enforce the alignment in a portable way, by making the array be a pointer array or the like.

[Oscar Cwajbaum]

Created attachment 13312 [details]
Fix ARM crash due to mis-alignment - rev2

[Oscar Cwajbaum]

Sounds good to me. I've attached a modified patch with Darin's suggestion.

[Maciej Stachowiak]

Comment on attachment 13312 [details]
Fix ARM crash due to mis-alignment - rev2

r=me

[Sam Weinig]

Landed in r19791.