The m4_ifblank macro is not available on CentOS 6, reverse conditionals
to allow use of m4_ifval instead.  ./bootstrap.sh was run but this patch
does not result in any difference to the generated configure script.

Change-Id: I280785deb872ed8d3339d99cce63a2b54d5f1438

Change-Id: I530c0a72f965437acef6a9a4fbfe5c487f078b65

This change causes the configure script to fail if the C compiler does
not support both function attributes constructor and destructor.  These
were already required as modules cannot function without these attributes
and Asterisk requires modules.

This also has AST_GCC_ATTRIBUTE set a variable
ax_cv_have_func_attribute_$1.  This is the same variable name used by
autoconf-archive's AX_GCC_FUNC_ATTRIBUTE, used for the same purpose.

Change-Id: Id68e8a1447f2a6d707c54b56350e7bfdb33fb663

GCC 4.7 Manual:
http://gcc.gnu.org/onlinedocs/gcc-4.7.4/gcc/Function-Attributes.html

weakref ("target")

A weak reference is an alias that does not by itself require a definition
to be given for the target symbol.

ASTERISK-22559 #close
Reported by: Ibercom

Change-Id: I36a136cae947b65187a697533416f9ff9a0b8cdf

Recent versions of autoconf (2.68 on my system) won't properly process the configure
script unless every call to AC_LANG_PROGRAM is m4-quoted. Many calls in the script
were, but many were not. This patch corrects the unquoted calls.
........

Merged revisions 350837 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 350838 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@350839 65c4cc65-6c06-0410-ace0-fbb531ad65f3

(closes issue #17654)
 Reported by: pprindeville
 Patches: 
       issue17654.diff uploaded by qwell (license 4)
 Tested by: qwell, pprindeville


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@276830 65c4cc65-6c06-0410-ace0-fbb531ad65f3

Review: https://reviewboard.asterisk.org/r/790/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@276731 65c4cc65-6c06-0410-ace0-fbb531ad65f3

Defaulting to 'static' for the function scope was bad... so remove it.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@201090 65c4cc65-6c06-0410-ace0-fbb531ad65f3

The last changes to ast_gcc_attribute.m4 caused some problems checking for
various attributes, because the scope of the symbol the attribute is applied
to can be important; this patch allows the scope to be specified for the check.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@200985 65c4cc65-6c06-0410-ace0-fbb531ad65f3

The configure script tests for compiler attributes didn't actually enable
enough warnings or provide a proper test harness to determine whether the 
compiler supports the attribute in question or not; this caused gcc 4.1 to
report that it supports 'weakref', but it doesn't actually support it in the
way that is needed for our optional API mechanism. The new configure script
test will properly distinguish between full support and partial support
for this attribute, among others.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@200764 65c4cc65-6c06-0410-ace0-fbb531ad65f3

improve handling of API calls provided by loaded modules through use of some GCC features; this makes app_stack's usage of AGI APIs even cleaner, and will allow it to work 'as expected' either with or without res_agi being loaded

reviewed at http://reviewboard.digium.com/r/62



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@159631 65c4cc65-6c06-0410-ace0-fbb531ad65f3

instead of trying to forcibly load res_agi when app_stack is loaded (even if the administrator didn't want it loaded), use GCC weak symbols to determine whether it was loaded already or not; if it was loaded, then use it.



git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@153709 65c4cc65-6c06-0410-ace0-fbb531ad65f3

https://origsvn.digium.com/svn/asterisk/branches/1.4

........
  r151240 | kpfleming | 2008-10-20 07:45:56 +0300 (Mon, 20 Oct 2008) | 3 lines
  
  break up acinclude.m4 into individual files, which will make it easier to maintain, easier to add new macros (less patching) and will ease maintenance of these macros across Asterisk branches
........


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@151242 65c4cc65-6c06-0410-ace0-fbb531ad65f3