[RFA/commit] pre-initialize python-value.c:values_in_python (bug in MacOS linker)

[RFA/commit] pre-initialize python-value.c:values_in_python (bug in MacOS linker)

[Joel Brobecker]

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Hello,

We noticed that GDB does not build on x86-macos and x86_64-macos when
configured --without-python (we found this out because one of our
machine no longer has python installed on it). The problem is that
the linker complains that it cannot file values_in_python, referenced
from value.c. This is a bug, since we verified that the symbol was
defined inside python-value.o which was also part of the archive.
We think that this might be related to the fact that the symbol is
defined as "C" (common). We changed the code to add an initial value
of NULL (which in C is strictly equivalent to the current code),
which changed our variable to the Data section and, ta da, allowed
GDB to link.

2008-12-05  Joel Brobecker  <brobecker@adacore.com>

        * python/python-value.c (values_in_python): Add specific initialization
        to NULL to work-around a MacOS linker bug.

Tested on x86-linux, both using --with-python and --without-python.
No regression.

I think this is pretty safe and safe contained, and doesn't reduce
the quality of the code, so I'm planning on committing this on Monday
when back from weekend holiday (I'm in Europe). Any objection? Should
I add a comment?

Thanks,
-- 
Joel

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diff --git a/gdb/python/python-value.c b/gdb/python/python-value.c
index 8bf4ec8..c17fb3b 100644
--- a/gdb/python/python-value.c
+++ b/gdb/python/python-value.c
@@ -30,7 +30,7 @@
    can copy the values' types if needed.  This is declared
    unconditionally to reduce the number of uses of HAVE_PYTHON in the
    generic code.  */
-struct value *values_in_python;
+struct value *values_in_python = NULL;
 
 #ifdef HAVE_PYTHON
 

Re: [RFA/commit] pre-initialize python-value.c:values_in_python (bug in MacOS linker)

[Tom Tromey]

>>>>> "Joel" == Joel Brobecker <brobecker@adacore.com> writes:

Joel> I think this is pretty safe and safe contained, and doesn't reduce
Joel> the quality of the code, so I'm planning on committing this on Monday
Joel> when back from weekend holiday (I'm in Europe). Any objection?

Not from me.  This is so small that I have trouble picturing anybody
objecting.

Joel> Should I add a comment?

I would appreciate that.

Tom

Re: [RFA/commit] pre-initialize python-value.c:values_in_python (bug in MacOS linker)

[Mark Kettenis]

> Date: Fri, 5 Dec 2008 19:41:23 +0100
> From: Joel Brobecker <brobecker@adacore.com>
> 
> Hello,
> 
> We noticed that GDB does not build on x86-macos and x86_64-macos when
> configured --without-python (we found this out because one of our
> machine no longer has python installed on it). The problem is that
> the linker complains that it cannot file values_in_python, referenced
> from value.c. This is a bug, since we verified that the symbol was
> defined inside python-value.o which was also part of the archive.
> We think that this might be related to the fact that the symbol is
> defined as "C" (common). We changed the code to add an initial value
> of NULL (which in C is strictly equivalent to the current code),
> which changed our variable to the Data section and, ta da, allowed
> GDB to link.
> 
> 2008-12-05  Joel Brobecker  <brobecker@adacore.com>
> 
>         * python/python-value.c (values_in_python): Add specific initialization
>         to NULL to work-around a MacOS linker bug.
> 
> Tested on x86-linux, both using --with-python and --without-python.
> No regression.
> 
> I think this is pretty safe and safe contained, and doesn't reduce
> the quality of the code, so I'm planning on committing this on Monday
> when back from weekend holiday (I'm in Europe). Any objection? Should
> I add a comment?

Ugh, Yuck.  Any idea if this is fixed in more recent versions of Mac OS X?

Re: [RFA/commit] pre-initialize python-value.c:values_in_python (bug in MacOS linker)

[Joel Brobecker]

> Ugh, Yuck.  Any idea if this is fixed in more recent versions of Mac OS X?

According to our sysadmin, we have the latest updates for Leopard,
and the latest stable release of Xcode. There might be a fix in the
latest developer patches released by Apple, but we're not sure.

-- 
Joel

Re: [RFA/commit] pre-initialize python-value.c:values_in_python (bug in MacOS linker)

[Joel Brobecker]

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> 2008-12-05  Joel Brobecker  <brobecker@adacore.com>
> 
>         * python/python-value.c (values_in_python): Add specific initialization
>         to NULL to work-around a MacOS linker bug.

Now checked in as attached (added a comment).

-- 
Joel

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Index: python/python-value.c
===================================================================
RCS file: /cvs/src/src/gdb/python/python-value.c,v
retrieving revision 1.5
diff -u -p -r1.5 python-value.c
--- python/python-value.c	28 Oct 2008 17:19:57 -0000	1.5
+++ python/python-value.c	8 Dec 2008 17:12:08 -0000
@@ -30,7 +30,9 @@
    can copy the values' types if needed.  This is declared
    unconditionally to reduce the number of uses of HAVE_PYTHON in the
    generic code.  */
-struct value *values_in_python;
+/* This variable is unnecessarily initialized to NULL in order to 
+   work around a linker bug on MacOS.  */
+struct value *values_in_python = NULL;
 
 #ifdef HAVE_PYTHON