[Bug 193795] Re: Printf inconsistency when handed null string
the gcc developers responded somewhat prick-like stating that it's the programmer's fault anyways the interim solution is to pass the -fno-builtin-printf to the compiler -- Printf inconsistency when handed null string https://bugs.launchpad.net/bugs/193795 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 193795] Re: Printf inconsistency when handed null string
I've traced the file that does the optimization to /usr/src/gcc-4.3/gcc-4.3.3/gcc/builtins.c The functions are fold_builtin_printf() fold_builtin_sprintf() the functions return a tree that seems to point straight to some puts() or putchar() construct that return tree should be modified to include a null check I'm posting this preliminary research in case anyone already knows the gcc tree struct and can easily patch it -- Printf inconsistency when handed null string https://bugs.launchpad.net/bugs/193795 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 193795] Re: Printf inconsistency when handed null string
I think you need to try to convince the gcc developers that this is a bug. -- Printf inconsistency when handed null string https://bugs.launchpad.net/bugs/193795 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
Re: [Bug 193795] Re: Printf inconsistency when handed null string
How can I do that? On Sun, May 10, 2009 at 3:29 AM, Malcolm Parsons malcolm.pars...@gmail.comwrote: I think you need to try to convince the gcc developers that this is a bug. -- Printf inconsistency when handed null string https://bugs.launchpad.net/bugs/193795 You received this bug notification because you are a direct subscriber of the bug. -- Printf inconsistency when handed null string https://bugs.launchpad.net/bugs/193795 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 193795] Re: Printf inconsistency when handed null string
How can I do that? You could try posting to their mailing list. http://gcc.gnu.org/lists.html -- Printf inconsistency when handed null string https://bugs.launchpad.net/bugs/193795 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 193795] Re: Printf inconsistency when handed null string
I've been digging through the gcc-4.3 source, looking for where the compiler swaps printf(%s\n,str); with puts(str); but the source is huge and I have no idea where or how to find the code responsible for this. I would happily patch this, provided I can get some direction on where I can find the optimization code -- Printf inconsistency when handed null string https://bugs.launchpad.net/bugs/193795 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 193795] Re: Printf inconsistency when handed null string
** Changed in: gcc-4.3 (Ubuntu) Status: Triaged = Confirmed -- Printf inconsistency when handed null string https://bugs.launchpad.net/bugs/193795 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 193795] Re: Printf inconsistency when handed null string
gcc optimises printf to puts. They behave differently, so the optimisation is invalid. ** Changed in: gcc-4.3 (Ubuntu) Sourcepackagename: glibc = gcc-4.3 -- Printf inconsistency when handed null string https://bugs.launchpad.net/bugs/193795 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 193795] Re: Printf inconsistency when handed null string
** Changed in: glibc (Ubuntu) Importance: Undecided = Low Status: New = Triaged -- Printf inconsistency when handed null string https://bugs.launchpad.net/bugs/193795 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 193795] Re: Printf inconsistency when handed null string
I can confirm this behaviour. I am not sure that you've correctly identified the cause, though. Looking at the disassembled machine code for both function calls, I found that 'printf(%s\n)' isn't handled by printf() at all -- the compiler inserts a call to puts() instead. puts(), in turn, calls strlen(), passing it a null pointer, which strlen() tries to dereference. Hence, the segmentation fault. One more thing: Is this actually a bug? I mean, the inconsistency is due to gcc's substituting puts() for printf(). Calling puts() with a null pointer results in a segfault. But isn't it the programmer's job to make sure that he doesn't accidentally pass a null pointer to puts() -- or to printf(%s\n) for that matter? Anyway, since I can reproduce this, I am marking this as confirmed. -- Printf inconsistency when handed null string https://bugs.launchpad.net/bugs/193795 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 193795] Re: Printf inconsistency when handed null string
I agree 100% that it is the programmer's responsibility to check for null pointers and found this bug through testing of my own code. I also played around with it last night and confirm as well that my original guess at the cause of this behavior was incorrect. The only reason I reported this behavior was because in the latter of the two cases above it doesn't segfault, but in the former does. I think that the behavior should be consistent whether it has the space or not. -- Printf inconsistency when handed null string https://bugs.launchpad.net/bugs/193795 You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 193795] Re: Printf inconsistency when handed null string
Small correction: vfprintf.c not vprintf.c. Sorry for the typo. -- Printf inconsistency when handed null string https://bugs.launchpad.net/bugs/193795 You received this bug notification because you are a member of Ubuntu Bugs, which is the bug contact for Ubuntu. -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
