Optimizer Bug in gcc 3.0, 3.3 and 3.4

Thu, 22 Sep 2005 08:41:08 -0700 

>Submitter-Id:  net
>Originator:    Friedemann Buergel
>Organization:  Weblaw AG, CH-3008 Bern, ++41-31-3805777, www.weblaw.ch
>Confidential:  no
>Synopsis:      Optimizer Bug in gcc 3.0, 3.3 and 3.4
>Severity:      critical
>Priority:      medium
>Category:      c
>Class:         wrong-code
>Release:       3.3.5 (Debian 1:3.3.5-13) (Debian stable)
>Environment:
System: Linux 2.4.18 #1 SMP Tue Jul 22 09:49:26 CEST 2003 i686 GNU/Linux
Architecture: i686
host: i486-pc-linux-gnu
build: i486-pc-linux-gnu
target: i486-pc-linux-gnu
configured with: ../src/configure -v --enable-languages=c,c++,java,f77,pascal,objc,ada,treelang --prefix=/usr --mandir=/usr/share/man --infodir=/usr/share/info --with-gxx-includ$ 
>Description:
gcc produces wrong code when optimizer (O1 O2 or O3) is used.
The c-source showing the problem is generated by the flex lexical scanner.
Applies to gcc versions 3.0.4, 3.3.5 and 3.4.4 (and maybe others not tested). 
Tested on Debian/Intel platforms only.
On gcc 2.95 and multiple former versions of gcc, the problem does not occur.

>How-To-Repeat:
       Unpack the attached archive, cd showbug, make.
It will first compile the program, then process and display some test data. 

       Prerequisites:
       You must have the flex lexical parser installed for this to work

       Expected behavior:
       Some HTML code shows up like <HTML lang="it"> <BODY> ...

       Actual behavior:
       The HTML is crippled so that the first
       character of many tags is missing, e.g. HTML ang="it"> BODY> ...
>Fix:
       No fix is known to me, workaround is -O0 or using gcc 2.95

Attachment: show-gcc-3.x-optimizer-bug.tar.gz
Description: application/tgz

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