[Poppler-bugs] [Bug 63067] Misuse of setjmp in DCTStream

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=63067

--- Comment #4 from Thomas Freitag <Thomas.Freitag at alfa.de> ---
(In reply to comment #0)
> According to POSIX and the C spec, `setjmp` should only be used as the
> "entire controlling expression" of a selection of iteration statement,
> possibly with `!` or `== 0` or similar.
> 
> But in DCTStream.cc is the line:
> 
>     if (!setjmp(err.setjmp_buffer) && jpeg_read_header(&cinfo, TRUE) !=
> JPEG_SUSPENDED)

This is NOT a iteration statement, iteration statements are "for", "while" and
similar!

> 
> If I'm not mistaken, that is undefined behavior. Not that it broke anything
> yet...
> 
> Instead it should be:
> 
>     if (!setjmp(err.setjmp_buffer))
>     {
>       if (jpeg_read_header(&cinfo, TRUE) != JPEG_SUSPENDED)

Okay, okay, the order of execution of an if condition is undefined in C/C++
(other than if Java, where You can count on that it will be done from left to
right). BUT I never see an c/c++ compiler which does it in another way.
But if we are puristic: Yes, it should be in that way!

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