[Webkit-unassigned] [Bug 89787] alignment crash in MIMESniffer

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=89787





--- Comment #4 from Yong Li <yoli at rim.com>  2012-07-11 15:02:27 PST ---
(In reply to comment #3)
> Another way to deal with this is add the slow case, which has no problem with unalignment, since everything is char* based:
> 
> diff --git a/Source/WebCore/platform/network/MIMESniffing.cpp b/Source/WebCore/platform/network/MIMESniffing.cpp
> index 5efd17f..f67adb5 100644
> --- a/Source/WebCore/platform/network/MIMESniffing.cpp
> +++ b/Source/WebCore/platform/network/MIMESniffing.cpp
> @@ -233,11 +233,33 @@ static inline size_t dataSizeNeededForImageSniffing()
>      return result;
>  }
> 
> +#if (CPU(ARM) || CPU(MIPS)) && COMPILER(GCC)
> +static inline bool maskedCompareSlowCase(const MagicNumbers& info, const char* data)
> +{
> +    const char* p = reinterpret_cast<const char*>(info.pattern);
> +    const char* m = reinterpret_cast<const char*>(info.mask);
> +    const char* d = reinterpret_cast<const char*>(data);
> +
> +    size_t count = info.size;
> +
> +    for (size_t i = 0; i < count; ++i) {
> +        if ((*d++ & *m++) != *p++)
> +            return false;
> +    }
> +    return true;
> +}
> +#endif
> +
>  static inline bool maskedCompare(const MagicNumbers& info, const char* data, size_t dataSize)
>  {
>      if (dataSize < info.size)
>          return false;
> 
> +#if (CPU(ARM) || CPU(MIPS)) && COMPILER(GCC)
> +    if (!isPointerTypeAlignmentOkay(data))
> +        return maskedCompareSlowCase(info, data);
> +#endif
> +
>      const uint32_t* pattern32 = reinterpret_cast_ptr<const uint32_t*>(info.pattern);
>      const uint32_t* mask32 = reinterpret_cast_ptr<const uint32_t*>(info.mask);
>      const uint32_t* data32 = reinterpret_cast_ptr<const uint32_t*>(data);


I prefer this solution to hacking the warning.

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