|Summary:||__isoc99_sscanf is used regardless of -std option|
|Product:||[Fedora] Fedora||Reporter:||Stas Sergeev <stsp2>|
|Component:||glibc||Assignee:||Andreas Schwab <schwab>|
|Status:||CLOSED NOTABUG||QA Contact:||Fedora Extras Quality Assurance <extras-qa>|
|Version:||13||CC:||fweimer, jakub, schwab|
|Fixed In Version:||Doc Type:||Bug Fix|
|Doc Text:||Story Points:||---|
|Last Closed:||2010-08-11 12:09:36 UTC||Type:||---|
|oVirt Team:||---||RHEL 7.3 requirements from Atomic Host:|
|Cloudforms Team:||---||Target Upstream Version:|
Description Stas Sergeev 2010-08-11 11:42:20 UTC
Description of problem: All my programs have suddenly started to use __isoc99_sscanf@@GLIBC_2.7, making it impossible to run them on an older systems without recompiling. The changelog of glibc says: Redirect to __isoc99_* if strict ISO C99 or POSIX conformance requested. But how to "unrequest" that strict conformance, other than by defining _GNU_SOURCE? -std=gnu89 doesn't help. Version-Release number of selected component (if applicable): glibc-2.12-3.x86_64 How reproducible: Always Steps to Reproduce: 1. Compile program with sscanf 2. Try to run it on another system with glibc <2.7 Actual results: /lib/libc.so.6: version `GLIBC_2.7' not found Expected results: Program works Additional info:
Comment 1 Jakub Jelinek 2010-08-11 12:09:36 UTC
glibc never pretended to be forward compatible, so if you want to run on system with older glibc, you should compile/link against the oldest glibc you want to support. To use the non-standard version of sscanf, you need -D_GNU_SOURCE, or e.g. -D_POSIX_C_SOURCE=199506L, as POSIX 2008 mode is now the default.
Comment 2 Stas Sergeev 2010-08-11 12:28:03 UTC
Yes, I understand the forward-compat is never guaranteed, but is the use of __isoc99_sscanf really intentional when -std=gnu89 is used?
Comment 3 Jakub Jelinek 2010-08-11 12:40:20 UTC
Yes. -std=gnu89 doesn't have very big influence on the content of glibc headers, all it means is that __STRICT_ANSI__ isn't defined. The Feature Test Macros is what matters. And, in case of *scanf, it is actually better if the %ac/%as/%a[ GNU extensions are never used any more, and %mc/%ms/%m[ is used instead. So, the more __isoc99_*scanf is used, the better.