From: "naruse (Yui NARUSE)" <naruse@...>
Date: 2013-03-12T15:10:43+09:00
Subject: [ruby-core:53329] [ruby-trunk - Bug #7756] clang 3.2 sees through UNINITIALIZED_VAR macro, gives warning


Issue #7756 has been updated by naruse (Yui NARUSE).


GCC 4.6 and clang (2.8?) supports pragma diagnostic, but its syntax is different from current UNINITIALIZED_VAR().

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wuninitialized"
blah blah
#pragma GCC diagnostic pop

http://gcc.gnu.org/gcc-4.6/changes.html
http://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Pragmas.html
http://clang.llvm.org/docs/UsersManual.html#controlling-diagnostics-via-pragmas
----------------------------------------
Bug #7756: clang 3.2 sees through UNINITIALIZED_VAR macro, gives warning
https://bugs.ruby-lang.org/issues/7756#change-37525

Author: drbrain (Eric Hodel)
Status: Open
Priority: Normal
Assignee: mame (Yusuke Endoh)
Category: core
Target version: next minor
ruby -v: -


=begin

In clang 3.2, the UNINITIALIZED_VAR macro does not prevent the compiler from producing a warning.

Apple clang 3.2:

  $ clang -v
  Apple LLVM version 4.2 (clang-425.0.24) (based on LLVM 3.2svn)
  Target: x86_64-apple-darwin12.2.1
  Thread model: posix

When compiling thread.c:

  compiling ../trunk/thread.c
  ../trunk/thread.c:3261:34: warning: variable 'orig_read' is uninitialized when
        used within its own initialization [-Wuninitialized]
      rb_fdset_t UNINITIALIZED_VAR(orig_read);
                                   ^~~~~~~~~
  ../trunk/vm_core.h:119:34: note: expanded from macro 'UNINITIALIZED_VAR'
  #define UNINITIALIZED_VAR(x) x = x
                                   ^
  ../trunk/thread.c:3262:34: warning: variable 'orig_write' is uninitialized when
        used within its own initialization [-Wuninitialized]
      rb_fdset_t UNINITIALIZED_VAR(orig_write);
                                   ^~~~~~~~~~
  ../trunk/vm_core.h:119:34: note: expanded from macro 'UNINITIALIZED_VAR'
  #define UNINITIALIZED_VAR(x) x = x
                                   ^
  ../trunk/thread.c:3263:34: warning: variable 'orig_except' is uninitialized when
        used within its own initialization [-Wuninitialized]
      rb_fdset_t UNINITIALIZED_VAR(orig_except);
                                   ^~~~~~~~~~~
  ../trunk/vm_core.h:119:34: note: expanded from macro 'UNINITIALIZED_VAR'
  #define UNINITIALIZED_VAR(x) x = x
                                   ^
  3 warnings generated.

=end



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