rpcrt4: Introduce a new function, safe_multiply, which will raise an exception if a multiply overflows a 4-byte integer.

[Robert Shearman]

Alexandre Julliard wrote:

>Robert Shearman <rob at codeweavers.com> writes:
>
>  
>
>>+    unsigned char overflow;
>>+#if defined(__i386__) && defined (__GNUC__)
>>+    __asm__(
>>+            "mull %3\n\t"
>>+            "seto %%cl"
>>+            : "=a" (ret), "=c" (overflow) /* outputs: eax, cl */
>>+            : "%a" (a), "rm" (b) /* inputs: eax, any register or memory
>>+                                  * address (params are interchangable) */
>>+            : "edx" /* edx clobbered */);
>>+#else
>>+    ret = a * b;
>>+    overflow = (b && (ret / b != a));
>>+#endif
>>    
>>
>
>That asm seems really overkill. Something like:
>
>  ULONGLONG ret = (ULONGLONG)a * b;
>  if (ret > 0xffffffff)
>
>will generate pretty much the same code with a recent gcc, and it's a
>lot more readable.
>  
>

Indeed it does. I'll resubmit the patch set with this change.

-- 
Rob Shearman