Bug 117991 – Fix cast-align warnings in FastMalloc.cpp

• Component: New Bugs
• Status: RESOLVED FIXED

[Csaba Osztrogonác]

/home/oszi/WebKit/Source/WTF/wtf/FastMalloc.cpp:3167:102: warning: cast from 'char*' to 'uint32_t* {aka unsigned int*}' increases required alignment of target type [-Wcast-align]
/home/oszi/WebKit/Source/WTF/wtf/FastMalloc.cpp:3167:194: warning: cast from 'char*' to 'uint32_t* {aka unsigned int*}' increases required alignment of target type [-Wcast-align]
/home/oszi/WebKit/Source/WTF/wtf/FastMalloc.cpp:3167:305: warning: cast from 'char*' to 'uint32_t* {aka unsigned int*}' increases required alignment of target type [-Wcast-align]
/home/oszi/WebKit/Source/WTF/wtf/FastMalloc.cpp:3167:52: warning: cast from 'char*' to 'uint32_t* {aka unsigned int*}' increases required alignment of target type [-Wcast-align]

3167: POISON_DEALLOCATION_EXPLICIT(ptr, size, startPoison, endPoison);

#define POISON_DEALLOCATION_EXPLICIT(allocation, allocationSize, startPoison, endPoison) do { \
    ASSERT((allocationSize) >= 2 * sizeof(uint32_t)); \
    reinterpret_cast<uint32_t*>(allocation)[0] = 0xbadbeef9; \
    reinterpret_cast<uint32_t*>(allocation)[1] = 0xbadbeefb; \
    if ((allocationSize) < 4 * sizeof(uint32_t)) \
        break; \
    reinterpret_cast<uint32_t*>(allocation)[2] = (startPoison) ^ PTR_TO_UINT32(allocation); \
    reinterpret_cast<uint32_t*>(allocation)[END_POISON_INDEX(allocationSize)] = (endPoison) ^ PTR_TO_UINT32(allocation); \
} while (false)

This define introduced in 
- https://trac.webkit.org/changeset/143488/trunk/Source/WTF/wtf/FastMalloc.cpp
- https://trac.webkit.org/changeset/143996/trunk/Source/WTF/wtf/FastMalloc.cpp

The question is that ptr in line 3167 is uint32_t aligned or not?

[Csaba Osztrogonác]

Could you check if they can be a valid warnings or can we suppress 
them with using reinterpret_cast_ptr instead of reinterpret_cast ?

[Csaba Osztrogonác]

any idea?

[Mark Hahnenberg]

(In reply to comment #2)
> any idea?

I think this one is okay to change to reinterpret_cast_ptr too because all FastMalloc allocations are guaranteed to be at least 8 byte aligned.

[Csaba Osztrogonác]

Created attachment 205919 [details]
Patch

[Csaba Osztrogonác]

(In reply to comment #3)
> (In reply to comment #2)
> > any idea?
> 
> I think this one is okay to change to reinterpret_cast_ptr too because all FastMalloc allocations are guaranteed to be at least 8 byte aligned.

Thanks, I attached the patch.

[Mark Hahnenberg]

Comment on attachment 205919 [details]
Patch

r=me

[Csaba Osztrogonác]

Comment on attachment 205919 [details]
Patch

Clearing flags on attachment: 205919

Committed r152349: <http://trac.webkit.org/changeset/152349>

[Csaba Osztrogonác]

All reviewed patches have been landed.  Closing bug.