[PATCH] D75056: [Driver] Default to -fno-common for all targets

[Hubert Tong via Phabricator via cfe-commits]

hubert.reinterpretcast added inline comments.


================
Comment at: clang/docs/ReleaseNotes.rst:87
 
+- -fno-common has been enabled as the default for all targets.
 
----------------
jyknight wrote:
> Might be nice to expand upon this somewhat, to give users a clue what it means to them.
> 
> E.g. 
> 
> Therefore, C code which uses multiple definitions of a global variable will trigger a multiple-definition linker errors. Generally this occurs when a variable in a header file neglects to use the "extern" keyword on the declaration. The previous behavior can be restored by specifying -fcommon.
Suggestion:
Therefore, C code that uses tentative definitions as definitions of a variable in multiple translation units will trigger multiple-definition linker errors. Generally, this occurs when the use of the `extern` keyword is neglected in the declaration of a variable in a header file. In some cases, no specific translation unit provides a definition of the variable. The previous behavior can be restored by specifying `-fcommon`.


CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D75056/new/

https://reviews.llvm.org/D75056