[MinGW-notify] [ mingw-Bugs-3555870 ] commctrl.h macros trigger -Waddress warnings in gcc 4.6.2

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Bugs item #3555870, was opened at 2012-08-09 16:46
Message generated for change (Comment added) made by joshtownzen
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Category: MinGW
Group: Behaves as Documented
Status: Closed
Resolution: Invalid
Priority: 5
Private: No
Submitted By: Josh Townzen (joshtownzen)
Assigned to: Nobody/Anonymous (nobody)
Summary: commctrl.h macros trigger -Waddress warnings in gcc 4.6.2

Initial Comment:
In gcc 4.6.2, the macros ListView_GetItemRect and ListView_GetSubItemRect in commctrl.h test that one of their arguments (the RECT pointer) is non-NULL before using it.  When you enable -Waddress (or -Wall) and pass a local RECT variable to either macro, this triggers a warning that the address can never be NULL.

OS:  Windows 7 32-bit

sh-3.1$ gcc -v
Using built-in specs.
COLLECT_GCC=C:\MinGW\BIN\gcc.exe
COLLECT_LTO_WRAPPER=c:/mingw/bin/../libexec/gcc/mingw32/4.6.2/lto-wrapper.exe
Target: mingw32
Configured with: ../gcc-4.6.2/configure --enable-languages=c,c++,ada,fortran,objc,obj-c++ --disable-sjlj-exceptions --with-dwarf2 --enable-shared --enable-libgomp --disable-win32-registry --enable-libstdcxx-debug --enable-version-specific-runtime-libs --build=mingw32 --prefix=/mingw
Thread model: win32
gcc version 4.6.2 (GCC)

sh-3.1$ ld -v
GNU ld (GNU Binutils) 2.22

Test program:

#include <windows.h>
#include <commctrl.h>

int main()
{
	RECT r;
 	ListView_GetItemRect(NULL, 0, &r, 0);
 	ListView_GetSubItemRect(NULL, 0, 0, 0, &r);

	return 0;
}

Compiled via:

g++ -o test.exe test.cpp -Waddress -D_WIN32_IE=0x0300

Compiler output:

test.cpp: In function 'int main()':
test.cpp:7:3: warning: the address of 'r' will always evaluate as 'true' [-Waddress]
test.cpp:8:3: warning: the address of 'r' will always evaluate as 'true' [-Waddress]


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Comment By: Josh Townzen (joshtownzen)
Date: 2012-10-26 14:29

Message:
The problem is that this is the proper way to use either of these two
macros; you create a local RECT variable and pass it to the macro to get
the result.  The caller isn't interested in the implementation details of
the macro, and shouldn't be getting a false-positive warning for using it
correctly.  I was hoping there was a way to rewrite the macros without
triggering this warning, though if there is, I haven't been able to find
it.

----------------------------------------------------------------------

Comment By: Earnie Boyd (earnie)
Date: 2012-10-26 13:56

Message:
Yes, the address of a variable will always be non zero.

----------------------------------------------------------------------

You can respond by visiting: 
https://sourceforge.net/tracker/?func=detail&atid=102435&aid=3555870&group_id=2435