[asterisk-bugs] [JIRA] (ASTERISK-21967) CFLAG Improvement to prevent compiler error in Virtual Machine environments

[PowerPBX (JIRA)]

PowerPBX created ASTERISK-21967:
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             Summary: CFLAG Improvement to prevent compiler error in Virtual Machine environments
                 Key: ASTERISK-21967
                 URL: https://issues.asterisk.org/jira/browse/ASTERISK-21967
             Project: Asterisk
          Issue Type: Improvement
      Security Level: None
          Components: Core/General
    Affects Versions: 11.4.0, 1.8.22.0
         Environment: CentOS 6 KVM Virtual Machine, Intel or AMD
            Reporter: PowerPBX


At some point not too long ago a default CFLAG setting for i386 and x86_64 optimization must have been changed.  It appears to now be too aggressive in some situations for some virtualization environments.  Asterisk compiles without error but fails to run.

See this issue for more explanation.
https://issues.asterisk.org/jira/browse/ASTERISK-20128

I have identified what I believe to be a solution to this problem.
In Asterisk 11.4.0, Makfile.rules, line 87-88

ifeq ($(findstring BUILD_NATIVE,$(MENUSELECT_CFLAGS)),BUILD_NATIVE)
    _ASTCFLAGS+=-march=native 

I believe this should be changed to:
ifeq ($(findstring BUILD_NATIVE,$(MENUSELECT_CFLAGS)),BUILD_NATIVE)
    _ASTCFLAGS+=-mtune=native

This appears to correct the problem in my limited testing. This flag is available since gcc v4.2.4 according to the gcc documentation at the link below.  Prior to that version the setting should probably be mtune=generic.   For even more universal compatibility perhaps the default should be mtune=generic.  That also corrected my problems and is even less likely to be a problem if I were to move my VPS to different hardware although is likely less optimal for newer CPU's.

http://gcc.gnu.org/onlinedocs/gcc-4.2.4/gcc/i386-and-x86_002d64-Options.html#i386-and-x86_002d64-Options 

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