Issue #6504 has been updated by Tomoyuki Chikanaga.

Related to Bug #8315: mkmf does not include include paths from pkg_config anymore added

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Backport #6504: mkmf.rb should not use CFLAGS when compiling C++ code
https://bugs.ruby-lang.org/issues/6504#change-48914

* Author: Hans de Graaff
* Status: Closed
* Priority: Normal
* Assignee: Tomoyuki Chikanaga
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mkmf.rb currently sets CXXFLAGS to include CFLAGS. It should not do this because CFLAGS are meant for C compilation only and may contain flags that cause problems with C++. If there are flags that are common to both C and C++ (such as the -I flags in the downstream bug) then these should be collected in a separate variable.

https://github.com/ruby/ruby/blob/trunk/lib/mkmf.rb#L1786

CXXFLAGS = $(CFLAGS) #{CONFIG['CXXFLAGS']}

For reference our downstream bug report that triggered this: https://bugs.gentoo.org/show_bug.cgi?id=396281



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