[issue24130] Remove -fno-common compile option from OS X framework builds?

[Ronald Oussoren]

Ronald Oussoren  added the comment:

I've checked and '-fcommon' is default (at least with Xcode 12 beta on x86_64), 
and likely not what you'd want:  With "-fcommon" the definition a non-static 
variable in two different files will get merged:

first.m:   int x;
second.m:   int x;

Without '-fno-common' this will be allowed (and that's generally not what you 
want, correct usage is to have one of the files use "extern int x;".  In clang 
11 "-fno-common" is enabled by default, but I don't know when Apple do this in 
their copy of clang.




I'm closing this issue because using -fno-common is necessary avoid having a 
common section in the framework (see msg243259)

--
resolution:  -> not a bug
stage: patch review -> resolved
status: open -> closed
type:  -> compile error

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[issue24130] Remove -fno-common compile option from OS X framework builds?

[Ronald Oussoren]

Ronald Oussoren added the comment:

According to [1] common symbols are not allowed in frameworks. I guess that's 
why we added '-fno-common' to the linker flags. 

[1] 
https://developer.apple.com/library/mac/documentation/MacOSX/Conceptual/BPFrameworks/Concepts/FrameworkBinding.html#//apple_ref/doc/uid/20002256-BAJICBDD

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[issue24130] Remove -fno-common compile option from OS X framework builds?

[Ned Deily]

Ned Deily added the comment:

Sorry, that second patch should have been:

diff -configure.ac
--- a/configure.ac  Tue May 05 12:04:35 2015 -0700
+++ b/configure.ac  Tue May 05 18:22:39 2015 -0700
@@ -2346,7 +2346,7 @@
Linux*|GNU*) LINKFORSHARED="-Xlinker -export-dynamic";;
# -u libsys_s pulls in all symbols in libsys
Darwin/*)
-   LINKFORSHARED="$extra_undefs -framework CoreFoundation"
+   LINKFORSHARED="-framework CoreFoundation"

# Issue #18075: the default maximum stack size (8MBytes) is too
# small for the default recursion limit. Increase the stack size

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[issue24130] Remove -fno-common compile option from OS X framework builds?

[Ned Deily]

New submission from Ned Deily:

As noted in msg242635 of issue23911, for some reason configure.ac adds the gcc 
-fno-common option for OS X framework builds.  Is this still necessary?  I'm 
guessing it might be vestigial code left over from the Mac toolbox support in 
Python 2 that was removed in Python 3.

diff configure.ac
--- a/configure.ac  Tue May 05 12:04:35 2015 -0700
+++ b/configure.ac  Tue May 05 16:47:34 2015 -0700
@@ -2101,9 +2101,6 @@
 AC_MSG_CHECKING(for --enable-framework)
 if test "$enable_framework"
 then
-   BASECFLAGS="$BASECFLAGS -fno-common -dynamic"
-   # -F. is needed to allow linking to the framework while
-   # in the build location.
AC_DEFINE(WITH_NEXT_FRAMEWORK, 1,
  [Define if you want to produce an OpenStep/Rhapsody framework
  (shared library plus accessory files).])

Also, there seems to be a unused reference to $extra_undefs left over in 
configure.ac from the removed Mac toolbox support:

--- a/configure.ac  Tue May 05 12:04:35 2015 -0700
+++ b/configure.ac  Tue May 05 18:20:21 2015 -0700
@@ -2346,8 +2346,6 @@
Linux*|GNU*) LINKFORSHARED="-Xlinker -export-dynamic";;
# -u libsys_s pulls in all symbols in libsys
Darwin/*)
-   LINKFORSHARED="$extra_undefs -framework CoreFoundation"
-
# Issue #18075: the default maximum stack size (8MBytes) is too
# small for the default recursion limit. Increase the stack size
# to ensure that tests don't crash

--
assignee: ned.deily
components: Build, Macintosh
messages: 242636
nosy: ned.deily, ronaldoussoren
priority: normal
severity: normal
stage: patch review
status: open
title: Remove -fno-common compile option from OS X framework builds?
versions: Python 3.5

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