This is the mail archive of the
gcc-bugs@gcc.gnu.org
mailing list for the GCC project.
[Bug c++/35835] New: Compiler fails to recognize match of local "extern" declarations
- From: "oder at eleks dot lviv dot ua" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 5 Apr 2008 18:33:08 -0000
- Subject: [Bug c++/35835] New: Compiler fails to recognize match of local "extern" declarations
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
Consider following program
======= begin of test.cpp ========
#include <stdio.h>
static inline void SetValue(int i)
{
extern int g_iValue;
g_iValue = i;
}
static inline int GetValue()
{
extern int g_iValue;
return g_iValue;
}
int g_iValue = 0;
int main()
{
int iValueSave = GetValue();
SetValue(1);
printf("%d\n", GetValue());
SetValue(iValueSave);
return 0;
}
======= end of test.cpp ========
I use this apptoach to only publish get/set global variable accessors in header
while keeping variable itself hidden in cpp.
If compiled with optimizations turned on, compiler fails identify two local
"extern" declarations as a single memory object and uses initial value
retrieved for iValueSafe in call to printf as well (as if SetValue() was
unrelated to g_iValue).
If compiled and run, program outputs 0 instead of 1.
osx-leopard:build oder$ g++ -O3 -o test test.cpp
osx-leopard:build oder$ ./test
0
Output of "g++ -v" is:
Using built-in specs.
Target: powerpc-apple-darwin9
Configured with: /var/tmp/gcc/gcc-5478~1/src/configure --disable-checking
-enable-werror --prefix=/usr --mandir=/share/man
--enable-languages=c,objc,c++,obj-c++
--program-transform-name=/^[cg][^.-]*$/s/$/-4.0/
--with-gxx-include-dir=/include/c++/4.0.0 --with-slibdir=/usr/lib
--build=powerpc-apple-darwin9 --host=powerpc-apple-darwin9
--target=powerpc-apple-darwin9
Thread model: posix
gcc version 4.0.1 (Apple Inc. build 5478)
--
Summary: Compiler fails to recognize match of local "extern"
declarations
Product: gcc
Version: 4.0.1
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c++
AssignedTo: unassigned at gcc dot gnu dot org
ReportedBy: oder at eleks dot lviv dot ua
GCC build triplet: ppc
GCC host triplet: ppc
GCC target triplet: ppc
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35835