Bug 40069 - SIGSEGV in program that uses an inlined operator[] with range checking, only with gcc 2.96 on intel, not on alpha
Summary: SIGSEGV in program that uses an inlined operator[] with range checking, only ...
Alias: None
Product: Red Hat Linux
Classification: Retired
Component: gcc
Version: 7.1
Hardware: i686
OS: Linux
Target Milestone: ---
Assignee: Jakub Jelinek
QA Contact: David Lawrence
Depends On:
TreeView+ depends on / blocked
Reported: 2001-05-10 13:06 UTC by Christoph Karle
Modified: 2007-04-18 16:33 UTC (History)
0 users

Clone Of:
Last Closed: 2001-05-16 16:44:39 UTC

Attachments (Terms of Use)
demo source code (1.99 KB, text/plain)
2001-05-10 13:10 UTC, Christoph Karle
no flags Details

Description Christoph Karle 2001-05-10 13:06:47 UTC
Description of Problem:
SIGSEGV occurs in a programm that uses a selfmade vector class for
complex<double> with an inline index operator with range checking.
the segfault does not occur directly in the index operator, but in
complex<double>::operator *= , which calls a __doaml() function, where
the segfault occurs in the first fldl machine instruction (at least gdb
says so). it seems that the address which fldl wants to access is illegal.
the segfault only occurs with range checking enabled (through a define)
  operator[] inlined, -O2 or -O3
  operator[] not inlined, -O3
and NOT with
  operator[] inlined, -O2/-O3 and -fno-inline
  operator[] not inlined, -O3 -fno-inline or -O2
it only occurs on intel with gcc 2.96 (i tried both rh 7.0 and 7.1).
on an ev67 alpha with rh 7.0 and gcc 2.96 everything is ok,
also with gcc 2.91.66 on intel.
this suggests that the problem is in the inline code generation in the
intel backend.

How Reproducible:
when the attached source code is compiled with gcc 2.96 on intel and
-O2 or -O3, the resulting program always aborts with a segfault.
slight changes in the operator[] (for example throwing an exception
instead of a cout/printf), or in the calculation that is done with the
vectors can prevent the segfault (more comments on this in the attached

Steps to Reproduce:
1. make sure VECTOR_DEBUG is defined in the source code
2. compile the program with
     g++ -O2 inlinebug.cpp -o inlinebug
3. exectute the program with

Actual Results:
  Segmentation fault (core dumped)

(the 0 is the index of the vector where the segfault occurs)

Expected Results:

(for a different size of the vector, the result would of course be different)

Additional Information:

Comment 1 Christoph Karle 2001-05-10 13:10:21 UTC
Created attachment 17987 [details]
demo source code

Comment 2 Jakub Jelinek 2001-05-10 14:01:40 UTC
Actually, it seems -fregmove related (-fno-regmove fixes it). Apparently
-fregmove decides to merge a /u register with a changeable one, debugging.

Comment 3 Jakub Jelinek 2001-05-16 16:44:34 UTC
Ouch, forgot to update status here:
I've fixed this with http://gcc.gnu.org/ml/gcc-patches/2001-05/msg00581.html
and it will be included in gcc-2.96-86.

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