Package: netpbm Version: 2:10.0-8sarge1 Severity: normal pnmnorm segfaults under certain circumstances, because of a mis-compilation by gcc -O3 on ppc. Recompiling the package with -O2 results in a working pnmnorm.
Reproducing the segfault is difficult because whether it occurs depends on a very obscure detail of its invocation. The buggy compiler inlines some stuff into main(), and generates code which uses the register r18 without initializing it. The value of r18 isn't predictable at that point because (here comes the fun part) nothing in the entire process has touched it, and it still holds whatever value was in it before the execve! The contents of r18 immediately before execve depend on what program is doing the exec. I have found that ash and bash are both more likely to lead to a segfault than zsh and tcsh. And if you try to chase this bug down with strace, its interception of execve() changes the registers enough to prevent (or perhaps, depending on how your strace was compiled, cause) the segfault. Best. Heisenbug. Ever.! It may also be kernel dependent (I doubt you can expect every kernel to leave r18 untouched all the way through execve.) This script causes the segfault reliably for me. #!/bin/ash pnmnorm <<EOF >/dev/null P2 4 2 255 56 118 168 182 0 0 0 0 EOF It also segfaults with bash, but ash is better for the demo because it makes the segfault glaringly obvious by printing "Segmentation fault", whereas bash makes you check $? to find out what happened. -- System Information: Debian Release: 3.1 Architecture: powerpc (ppc) Kernel: Linux 2.6.11-powerpc Locale: LANG=C, LC_CTYPE=C (charmap=ANSI_X3.4-1968) Versions of packages netpbm depends on: ii bc 1.06-15 The GNU bc arbitrary precision cal ii libc6 2.3.2.ds1-22 GNU C Library: Shared libraries an ii libjpeg62 6b-10 The Independent JPEG Group's JPEG ii libnetpbm10 2:10.0-8sarge1 Shared libraries for netpbm ii libpng12-0 1.2.8rel-1 PNG library - runtime ii libtiff4 3.7.2-3 Tag Image File Format (TIFF) libra ii zlib1g 1:1.2.2-4.sarge.2 compression library - runtime -- no debconf information -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]
