| Summary: | C++ with -malign-double SEGVs; egcs-c++-1.1.2, RH6.0 | ||
|---|---|---|---|
| Product: | [Retired] Red Hat Linux | Reporter: | jason.wm.mitchell |
| Component: | egcs | Assignee: | Cristian Gafton <gafton> |
| Status: | CLOSED NOTABUG | QA Contact: | |
| Severity: | medium | Docs Contact: | |
| Priority: | medium | ||
| Version: | 6.0 | CC: | jason.wm.mitchell |
| Target Milestone: | --- | ||
| Target Release: | --- | ||
| Hardware: | i386 | ||
| OS: | Linux | ||
| URL: | http://chico.hm.uc.edu/~jmitchel/linux/malign-double/ | ||
| Whiteboard: | |||
| Fixed In Version: | Doc Type: | Bug Fix | |
| Doc Text: | Story Points: | --- | |
| Clone Of: | Environment: | ||
| Last Closed: | 1999-07-30 13:08:35 UTC | Type: | --- |
| Regression: | --- | Mount Type: | --- |
| Documentation: | --- | CRM: | |
| Verified Versions: | Category: | --- | |
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |
| Cloudforms Team: | --- | Target Upstream Version: | |
This issue has been forwarded to a developer for further action. *** This bug has been marked as a duplicate of 3777 *** Cristian, did you have any reason for marking this as a duplicate of 3777? As nearly as I can tell, the two have nothing to do with each other. Changing the setting of -malign-double changes the calling
conventions; therefore you must recompile all libraries if
you use this option. From the manual:
*Warning:* if you use the `-malign-double' switch, structures
containing the above types will be aligned differently than the
published application binary interface specifications for the
386.
[Re: alignment differences from pub'ed ABI] I am/was fully aware of this, but I don't think it makes any difference to the problem. The difficulty is that in my original 5.2 configuration, -malign-double worked fine, and provided some significant performance improvements, since my apps are all FP intensive. When I attempted the 6.0 upgrade (several ways), it failed miserably, even on simple test programs which I provided links to for any investigator's convenience. I think a resolution of DISGARD is an ineffective solution based on assuming that a warning negates use of the option. For me, it means a difference of waiting an extra hour or so for each of my runs; consider that I have about 4 * 64 individual programs that must run for a complete data set. I hope you will reconsider this resolution. -Jason |
The -malign-double switch no longer functions correctly with egcs-c++-1.1.2. C++ code compiled with this switch, then linked, SEGVs; dying somewhere in the streams library. This is demonstrated with a trivial test program: #include <cassert> #include <fstream> #include <iostream> #include <string> int main() { using namespace std; string name, value; ifstream ifs( "input.dat" ); assert( ifs.good() ); while( ifs >> value >> name ) cout << name << "\t" << value << endl; return( 0 ); } If -O0 is specified, the SEGV generally occurs in the istream constructor; on the manipulators flush, width or precision; or operator<<(). Specifying -Ox, x > 0, usually causes SEGV from ifstream::~ifstream(). Linking -static may prevent the SEGV in some instances with optimization, but I have not tested this extensively. Since the failure is a SEGV, there is little guarantee that the location of the signal will provide useful information The platforms tested were: 1. i686 tweaked RH5.2 (to run egcs/pgcc*-1.1.1) upgraded to RH6.0 2. i486 stock RH5.2 upgraded to RH6.0 3. i486 clean install of RH6.0 4. i586 clean install of RH6.0 The -malign-double option worked with egcs*-1.1.1. There is no apparent negative effect on plain C code compiled with the -malign-double switch. The test program and input data file, a makefile, verbose assembler with diffs, egcs-c++-1.1.2 -v -a output(make.out), and this description are available from: http://chico.hm.uc.edu/~jmitchel/linux/malign-double/ -jason ------- Additional Comments From 06/04/99 16:39 ------- I failed to specify that -malign-double option worked with egcs*-1.1.1 on RedHat 5.2 with glibc-2.1-0.990222, binutils-2.9.1.0.23-1, and libstdc++-2.9.0-7.