svn commit: samba r22731 - in branches/SAMBA_3_0/source: . tests
derrell at samba.org
derrell at samba.org
Mon May 7 17:37:13 GMT 2007
"Stefan (metze) Metzmacher" <metze at samba.org> writes:
> derrell at samba.org schrieb:
>> Author: derrell
>> Date: 2007-05-07 03:02:24 +0000 (Mon, 07 May 2007)
>> New Revision: 22731
>> WebSVN: http://websvn.samba.org/cgi-bin/viewcvs.cgi?view=rev&root=samba&rev=22731
>> - Fix bug #4594.
>> configure.in determines if -Werror-implicit-function-declaration is
>> available, and if so it enables that flag if --enable-developer is
>> specified. Since the configure tests themselves did not use that flag, it
>> was possible for a configure test to succeed, followed by a failed
>> compilation due to a facility being available but not having a proper
>> declaration in a header file. (This bit me with readahead().) This patch
>> ensures that if implicit function declarations will kill the build, the
>> feature being tested is deselected so the build will succeed.
>> The autoconf manual suggests using return instead of exit in configure
>> tests because the declaration for exit is often missing. We require this
>> now, since we error if prototypes are missing. See section 5.5.1 of
>> http://www.gnu.org/software/autoconf/manual/autoconf.html. This patch makes
>> these changes, because in fact, an external declaration for exit is missing
>> here (and likely elsewhere).
>> I've verified that the features selected (here) with the original
>> configure.in and the new one are the same except for, in my case,
>> readahead. I've also confirmed that the generated Makefile is identical.
>> These changes are not being applied to the 3.0.26 branch because it does not
>> exhibit the initial problem this patch is supposed to solve since it doesn't
>> attempt to use -Werror-implicit-function-declaration.
> Hi Derell,
> I don't think it's correct to use -Werror-implicit-function-declaration
> within the configure checks. Because the configure result now may
> differs between the normal and developer build.
Yes, that's exactly what I want (need) to do. The configure tests must differ
between the builds so that functions which are available during a
non-developer build will be used, whereas functions that will cause the
compile to barf during a developer build are excluded during a developer
> The correct fix would be to use a AC_CHECK_DECL() or AC_HAVE_DECL()
> for the specific function.
The problem is that these macros use whatever CFLAGS are defined. If
-Werror-implicit-function-declaration is not defined in CFLAGS during
configure, configure will determine that a function is available when in fact,
during a compile with -Werror-implicit-function-declaration, the compile will
fail. I don't think it's appropriate for configure to decide a feature should
be used when using it causes the compile to barf. This is exactly the case I
encountered. readahead() is available on my system, but is not declared in a
header file, similarly to exit(). Without that flag, a developer configure
will determine that readahead() is available but a compile will fail. By
consistently testing for and using the warnings-are-errors flag, the problem
is eliminated. During a developer build, readahead() is found to _not_ exist
so the compilation works fine. During a production build, readahead() is
found to exist and the compilation works fine since it doesn't use the
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