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[patch #6848] ac_c_printf_thsep.m4: Does ac_try_compile suffice?
From: |
Peter Simons |
Subject: |
[patch #6848] ac_c_printf_thsep.m4: Does ac_try_compile suffice? |
Date: |
Sun, 27 Dec 2009 11:24:04 +0000 |
User-agent: |
Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.1.6) Gecko/20091216 Shiretoko/3.5.6 |
Update of patch #6848 (project autoconf-archive):
Status: In Progress => Done
Open/Closed: Open => Closed
_______________________________________________________
Follow-up Comment #3:
The macro in its current form has been marked obsolete, because it cannot
reliably detect whether %' is supported or not. The fact that false positive
results may occur is particularly unpleasant. In order to be reliable, the
macro would have to test a cascade of properties:
1) Does the compiler fail to translate a broken %s or %d format string?
2) Does the compiler fail to translate a broken %' format string?
3) Does the compiler translate a proper %' format string?
4) When run, does sprinf() generate the expected result for %'?
Now, if running test programs is fine, then testing properties (3) and (4)
suffices to determine a result.
If test programs cannot be run, i.e. because the build takes place in a
cross-compilation environment, then properties (1), (2), and (3) can be tested
to determine a result that is not quite perfect -- because the target
platform's libc might still be broken --, but at least we know for certain (no
false-positives) that the *compiler* does recognize %' in format strings.
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