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| 64bit fix for jpgalleg |
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tobing
Member #5,213
November 2004
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Hi allegators, when compiling with MSVC 7.1 and enabled warnings for 64bit issues, I have seen that extern void _jpeg_chunk_puts(unsigned char *, int); should be changed to extern void _jpeg_chunk_puts(unsigned char *, size_t); in internal.h and io.c. Do you need a patch file for this? Should I send a mail to the AD mailing list? |
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Goalie Ca
Member #2,579
July 2002
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It is actually a signedness warning and would affect 32-bit platforms as well. strlen returns size_t while the function takes an int. I checked in the fix and chose to cast the line to (int). This doesn't change the logic, just gets rid of the warning. This is just a com chunk in the jpeg file header. The rest of the file/logic would need to be converted to size_t to get > 2GB files. I don't suppose the jpeg spec event supports that. ------------- |
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tobing
Member #5,213
November 2004
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Well, thanks... Of course that is one way of doing it, and it's no problem in regard of the file sizes. |
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Goalie Ca
Member #2,579
July 2002
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Well in this case (int) strlen won't cause a negative number. And negative numbers wouldn't do anything anyways.. it would be like sending a zero. I opted to not change anything instead of looking for all the loops and counters that use int instead of size_t. Sometimes it can be nice to have ssize_t for crazy pointer arith too. Anyways, thanks for pointing out the warning. ------------- |
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tobing
Member #5,213
November 2004
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Quote: Well in this case (int) strlen won't cause a negative number. That's right... Quote: And negative numbers wouldn't do anything anyways.. it would be like sending a zero. but this is not, if you look at the code: for (; size; size--) _jpeg_chunk_putc(*s++);
IF size is negative, then this loop would have many iterations until overflow, then counts down another 2 billion iterations. |
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Goalie Ca
Member #2,579
July 2002
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You're right.. I forgot what the code was again. I had pictured a while loop instead. ------------- |
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One thing might be considered though: using int would also accept negative values, which would be an error. Having the unsigned type in the argument list, it would be a lot harder to call it wrong. Well, probably not an issue though, because it's an internal function...