Bug 228744
| Summary: | gdb unexplained memory access at 0x0 | ||
|---|---|---|---|
| Product: | [Fedora] Fedora | Reporter: | Tom Stevelt <tms_olt> |
| Component: | gcc | Assignee: | Alexandre Oliva <aoliva> |
| Status: | CLOSED UPSTREAM | QA Contact: | |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | 9 | CC: | cagney, jan.kratochvil, lfrocha+rhbugzilla, triage |
| Target Milestone: | --- | ||
| Target Release: | --- | ||
| Hardware: | i386 | ||
| OS: | Linux | ||
| Whiteboard: | bzcl34nup | ||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 2008-10-13 15:02:51 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: | |||
| Bug Depends On: | |||
| Bug Blocks: | 173278 | ||
Yes, you are right.
It is a GCC Bug, though, regarding its DWARF generation.
ECX is a volatile (callee unsaved) register which currently gets referenced:
<2><162>: Abbrev Number: 6 (DW_TAG_formal_parameter)
DW_AT_name : argc
DW_AT_location : 2 byte block: 71 0 (DW_OP_breg1: 0)
<2><171>: Abbrev Number: 6 (DW_TAG_formal_parameter)
DW_AT_name : argv
DW_AT_location : 2 byte block: 71 4 (DW_OP_breg1: 4)
(breg1==ECX)
Fortunately if you use argc/argv more in main() it gets saved more persistently
and the bug gets no longer exposed.
Related Bug / Jakub's comment upstream:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=29628#c1
*** Bug 250414 has been marked as a duplicate of this bug. *** Based on the date this bug was created, it appears to have been reported against rawhide during the development of a Fedora release that is no longer maintained. In order to refocus our efforts as a project we are flagging all of the open bugs for releases which are no longer maintained. If this bug remains in NEEDINFO thirty (30) days from now, we will automatically close it. If you can reproduce this bug in a maintained Fedora version (7, 8, or rawhide), please change this bug to the respective version and change the status to ASSIGNED. (If you're unable to change the bug's version or status, add a comment to the bug and someone will change it for you.) Thanks for your help, and we apologize again that we haven't handled these issues to this point. The process we're following is outlined here: http://fedoraproject.org/wiki/BugZappers/F9CleanUp We will be following the process here: http://fedoraproject.org/wiki/BugZappers/HouseKeeping to ensure this doesn't happen again. I still have the same problem, that I reported in #250414. Fedora 8: glibc-2.7-2 gcc-4.1.2-33 gdb-6.6-45.fc8 Note that the bug I reported, closed as duplicate of this one, was reported for Fedora 7, not yet EOL. Same problem with fedora 9 preview: glibc-2.8-3.i686 gcc-4.3.0-8.i386 gdb-6.8-1.fc9.i386 Changing version to '9' as part of upcoming Fedora 9 GA. More information and reason for this action is here: http://fedoraproject.org/wiki/BugZappers/HouseKeeping It is fixed in the current upstream snapshot:
GNU C (GCC) version 4.4.0 20081007 (experimental) (x86_64-unknown-linux-gnu)
compiled by GNU C version 4.4.0 20081007 (experimental), GMP version 4.2.2, MPFR version 2.3.1.
Breakpoint 1, getargs (argc=1, argv=0xffffc514) at rh228744.c:5
5 printf ( "argc %d\n", argc ); /* set breakpoint here */
Missing separate debuginfos, use: debuginfo-install glibc.i686
(gdb) bt
#0 getargs (argc=1, argv=0xffffc514) at rh228744.c:5
#1 0x0804844e in main (argc=1, argv=0xffffc514) at rh228744.c:14
(gdb) n
argc 1
6 printf ( "filename %s\n", argv[1] );
(gdb) bt
#0 getargs (argc=1, argv=0xffffc514) at rh228744.c:6
#1 0x0804844e in main (argc=1, argv=0xffffc514) at rh228744.c:14
Closing this Bug as not so serious while it should be present in Fedora gcc-4.4.
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GDB throws an unexplained "cannot access memory at 0x0" after accessing argc or argv[] in a subsidary function. gdb-6.5-15.fc6.src.rpm How reproducible: always Steps to Reproduce: 1. run attached program using gdb. 2. set a breakpoint on line 6 ( getargs: printf ... argc ) 3. run, giving the name of any existing file 4. at breakpoint, execute bt (backtrace) and examine the output, which looks normal. 5. execute n (next) 6. execute another bt and see the messed up output which includes "cannot access memeory at 0x0". Actual results: (gdb) bt #0 getargs (argc=2, argv=0xbfe1a7b4) at foo6.c:7 #1 0x080483e5 in main (argc=Cannot access memory at address 0x0 ) at foo6.c:17 Expected results: (gdb) bt #0 getargs (argc=2, argv=0xbfe1a7b4) at foo6.c:6 #1 0x080483e5 in main (argc=2, argv=0xbfe1a7b4) at foo6.c:17 Additional info: Problem occures wiht either argc or argv. If you uncomment either of the printf statements in main(), then the problem in getargs goes away. Here is the source code. #include <stdio.h> void getargs ( int argc, char *argv[] ) { printf ( "argc %d\n", argc ); /* set breakpoint here */ printf ( "filename %s\n", argv[1] ); printf ( "hello world\n" ); } int main ( int argc, char *argv[] ) { // printf ( "argc %d\n", argc ); // printf ( "filename %s\n", argv[1] ); getargs ( argc, argv ); return ( 0 ); }