Bug 187540
| Summary: | Using any explicit optimization level results in an executable that fails with 'segmentation fault.' | ||
|---|---|---|---|
| Product: | [Fedora] Fedora | Reporter: | John Slayton <juanslayton> |
| Component: | gcc4 | Assignee: | Jakub Jelinek <jakub> |
| Status: | CLOSED NOTABUG | QA Contact: | |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | 4 | ||
| Target Milestone: | --- | ||
| Target Release: | --- | ||
| Hardware: | i386 | ||
| OS: | Linux | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2006-04-03 12:26:47 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
| Embargoed: | |||
| Attachments: | |||
Created attachment 127149 [details]
Tarball will create directory 'bugstash' which contains source greader.c and data files needed to run the executable. Also included are two executables from my machine, with/without -O2
That's just buggy testcase:
in download_roster, there is
char zo[2];
...
(not initialized in any way), then:
for (a = 0; a < Class_size; a++)
{
strcpy (Buf, "/tmp/bugstash/Name");
zo[0] = (char)((a / 10) + 48);
strcat (Buf, &zo[0]);
zo[0] = (char) ((a % 10) + 48);
strcat (Buf, &zo[0]);
fp = fopen(Buf, "r");
fgets (Name[a], 500, fp);
fclose(fp);
}
That triggers undefined behavior, can work only if zo[1] happens to have value 0,
but nothing initialized it that way.
|
Description of problem: Compiling source 'greader.c' with default optimization, program compiles cleanly with no errors or warnings, and runs properly. Trying to compile with explicit optimization (as 'gcc -lncurses -O2 greader.c'), program still compiles and exits cleanly with no errors or warnings. However, resulting executable fails on invocation with error message 'segmentation fault'. This happens when run on a Compaq Presario 5050 under Fedora Core(2.6.11-1.1369_FC4), using gcc version 4.0.0 20050519 (Red Hat 4.0.0-8). This last according to 'gcc --version'; dmesg gives a slightly different 'gcc version 4.0.0 20050525 (Red Hat 4.0.0-9)'. When run under Slackware 10 (Linux 2.4.26) with gcc version 3.3.4, this code compiles and runs properly with or without explicit optimization settings. I didn't fit in everything below; just let me say that after unfolding the attached tarball, you should be able to invoke the program with '/bugstash/greader_default'. Version-Release number of selected component (if applicable): How reproducible: Steps to Reproduce: 1. 2. 3. Actual results: Expected results: Additional info: