[Asterisk-code-review] Update configure.ac/Makefile for clang (asterisk[13])

[Diederik de Groot]

Hello Matt Jordan, Joshua Colp, Corey Farrell,

I'd like you to reexamine a change.  Please visit

    https://gerrit.asterisk.org/157

to look at the new patch set (#13).

Change subject: Update configure.ac/Makefile for clang
......................................................................

Update configure.ac/Makefile for clang

Created autoconf/ast_check_raii.m4: contains AST_CHECK_RAII which
checks compiler requirements for RAII:
gcc: -fnested-functions support
clang: -fblocks (and if required -lBlocksRuntime)
The original check was implemented in configure.ac and now has it's
own file. This function also sets C_COMPILER_FAMILY to either gcc or
clang for use by makefile

Created autoconf/ast_check_strsep_array_bounds.m4 (contains
AST_CHECK_STRSEP_ARRAY_BOUNDS):
which checks if clang is able to handle the optimized strsep & strcmp
functions (linux). If not, the standard libc implementation should be
used instead. Clang + the optimized macro's work with:
strsep(char *, char []), but not with strsepo(char *, char *).
Instead of replacing all the occurences throughout the source code,
not using the optimized macro version seemed easier

See 'define __strcmp_gc(s1, s2, l2) in bits/string2.h':
llvm-comment: Normally, this array-bounds warning are suppressed for
macros, so that unused paths like the one that accesses __s1[3] are
not warned about.  But if you preprocess manually, and feed the
result to another instance of clang, it will warn about all the
possible forks of this particular if statement. Instead of switching
of this optimization, another solution would be to run the preproces-
sing step with -frewrite-includes, which should preserve enough
information so that clang should still be able to suppress the diag-
nostic at the compile step later on.

See also "https://llvm.org/bugs/show_bug.cgi?id=20144"
See also "https://llvm.org/bugs/show_bug.cgi?id=11536"

Makefile.rules: If C_COMPILER_FAMILY=clang then add two warning
suppressions:
-Wno-unused-value
-Wno-parentheses-equality
In an earlier review (reviewboard: 4550 and 4554), they were deemed a
nuisace and less than benefitial.

configure.ac:
Added AST_CHECK_RAII() see earlier
Added AST_CHECK_STRSEP_ARRAY_BOUNDS() see earlier
Removed moved content

ASTERISK-24917
Change-Id: I12ea29d3bda2254ad3908e279b7effbbac6a97cb
---
M Makefile.rules
A autoconf/ast_check_raii.m4
A autoconf/ast_check_strsep_array_bounds.m4
M configure
M configure.ac
M include/asterisk/autoconfig.h.in
M makeopts.in
7 files changed, 299 insertions(+), 108 deletions(-)


  git pull ssh://gerrit.asterisk.org:29418/asterisk refs/changes/57/157/13
-- 
To view, visit https://gerrit.asterisk.org/157
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Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I12ea29d3bda2254ad3908e279b7effbbac6a97cb
Gerrit-PatchSet: 13
Gerrit-Project: asterisk
Gerrit-Branch: 13
Gerrit-Owner: Diederik de Groot <dkgroot at talon.nl>
Gerrit-Reviewer: Corey Farrell <git at cfware.com>
Gerrit-Reviewer: Diederik de Groot <dkgroot at talon.nl>
Gerrit-Reviewer: Joshua Colp <jcolp at digium.com>
Gerrit-Reviewer: Mark Michelson <mmichelson at digium.com>
Gerrit-Reviewer: Matt Jordan <mjordan at digium.com>