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* [Bug c/42643] "may be used uninitialized" compiled with "-Wall -O"
[not found] <bug-42643-4@http.gcc.gnu.org/bugzilla/>
@ 2012-01-06 20:09 ` mi+gcc at aldan dot algebra.com
2012-12-28 21:27 ` steven at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: mi+gcc at aldan dot algebra.com @ 2012-01-06 20:09 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42643
--- Comment #2 from mi+gcc at aldan dot algebra.com 2012-01-06 20:08:54 UTC ---
Created attachment 26259
--> http://gcc.gnu.org/bugzilla/attachment.cgi?id=26259
Live test case (file from Mozilla's NSS package)
Even when using gcc-4.6 (more specifically gcc version 4.6.3 20111104
(prerelease) (FreeBSD Ports Collection)), I still get a bogus warning on the
attached file, unless the optimization level is at -O3 AND the -fPIC is not
specified:
mi@narawntapu:nss/lib/util (1778) gcc46 -Wall -O3 -c nssb64e.i
mi@narawntapu:nss/lib/util (1779) gcc46 -Wall -O2 -c nssb64e.i
nssb64e.i: In function 'NSSBase64_EncodeItem_Util':
nssb64e.i:3239:15: warning: 'out_len' may be used uninitialized in this
function [-Wuninitialized]
mi@narawntapu:nss/lib/util (1780) gcc46 -Wall -O3 -fPIC -c nssb64e.i
nssb64e.i: In function 'NSSBase64_EncodeItem_Util':
nssb64e.i:3239:15: warning: 'out_len' may be used uninitialized in this
function [-Wuninitialized]
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c/42643] "may be used uninitialized" compiled with "-Wall -O"
[not found] <bug-42643-4@http.gcc.gnu.org/bugzilla/>
2012-01-06 20:09 ` [Bug c/42643] "may be used uninitialized" compiled with "-Wall -O" mi+gcc at aldan dot algebra.com
@ 2012-12-28 21:27 ` steven at gcc dot gnu.org
1 sibling, 0 replies; 3+ messages in thread
From: steven at gcc dot gnu.org @ 2012-12-28 21:27 UTC (permalink / raw)
To: gcc-bugs
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42643
Steven Bosscher <steven at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
CC| |mi+gcc at aldan dot
| |algebra.com
Resolution| |FIXED
--- Comment #3 from Steven Bosscher <steven at gcc dot gnu.org> 2012-12-28 21:27:07 UTC ---
(In reply to comment #2)
> Created attachment 26259 [details]
> Live test case (file from Mozilla's NSS package)
>
> Even when using gcc-4.6 (more specifically gcc version 4.6.3 20111104
> (prerelease) (FreeBSD Ports Collection)), I still get a bogus warning on the
> attached file, unless the optimization level is at -O3 AND the -fPIC is not
> specified:
>
> mi@narawntapu:nss/lib/util (1778) gcc46 -Wall -O3 -c nssb64e.i
> mi@narawntapu:nss/lib/util (1779) gcc46 -Wall -O2 -c nssb64e.i
> nssb64e.i: In function 'NSSBase64_EncodeItem_Util':
> nssb64e.i:3239:15: warning: 'out_len' may be used uninitialized in this
> function [-Wuninitialized]
> mi@narawntapu:nss/lib/util (1780) gcc46 -Wall -O3 -fPIC -c nssb64e.i
> nssb64e.i: In function 'NSSBase64_EncodeItem_Util':
> nssb64e.i:3239:15: warning: 'out_len' may be used uninitialized in this
> function [-Wuninitialized]
Why is this warning "bogus" in your opinion? It looks valid to me...
The compiler cannot tell that out_len is initialized. The only place
where out_len can pick up a value, is in the call to PL_Base64EncodeBuffer:
dummy = PL_Base64EncodeBuffer (inItem->data, inItem->len, 64,
out_string, max_out_len, &out_len);
The compiler can't look into PL_Base64EncodeBuffer to see if a value will
be assigned to "PRUint32 * output_destlen". The programmer can see that
this will happen, or that otherwise NULL will be returned, but that is a
really hard problem for the compiler. If you expect it to do that, you
should be looking for a static checker that can do this kind of expensive
analysis. There are GCC plugins that can do it.
FWIW the test case of comment #0 is fixed since GCC 4.6, so closing this
problem report as FIXED.
^ permalink raw reply [flat|nested] 3+ messages in thread
* [Bug c/42643] "may be used uninitialized" compiled with "-Wall -O"
2010-01-07 0:48 [Bug c/42643] New: " numidee at synopsys dot com
@ 2010-04-21 0:29 ` davidxl at gcc dot gnu dot org
0 siblings, 0 replies; 3+ messages in thread
From: davidxl at gcc dot gnu dot org @ 2010-04-21 0:29 UTC (permalink / raw)
To: gcc-bugs
------- Comment #1 from davidxl at gcc dot gnu dot org 2010-04-21 00:29 -------
(In reply to comment #0)
> When compiling the source with "-Wall -O", gcc gives the following warning:
>
> % gcc -c -Wall -O gcc_test.c
> gcc_test.c: In function ?functionLeon?:
> gcc_test.c:11: warning: ?reference? may be used uninitialized in this function
>
> % cat gcc_test.c
> #include<stdio.h>
>
> typedef struct {
> int yb;
> } TCRData;
>
> void functionLeon (TCRData *pParent, int pBool);
> void functionLeon (TCRData *pParent, int pBool)
> {
> int isRootCell;
> TCRData *reference;
>
> isRootCell = (pParent == NULL);
>
> if (!isRootCell)
> reference = pParent;
>
> if (pBool) {
> if(!isRootCell)
> reference->yb++;
> }
> }
>
> % gcc -v
> Using built-in specs.
> Target: x86_64-redhat-linux
> Configured with: ../../src/gcc-4.4.0/configure
> --prefix=/remote/depotsrc/depotsrc/amd64-2.4/local_install/gcc-4.4.0
> --enable-bootstrap --enable-shared --enable-threads=posix --disable-checking
> -with-gmp=/remote/depotsrc/depotsrc/amd64-2.4/local_install/gmp-4.3.1
> --with-mpfr=/remote/depotsrc/depotsrc/amd64-2.4/local_install/mpfr-2.4.1
> --with-system-zlib --enable-__cxa_atexit --disable-libunwind-exceptions
> --enable-languages=c,c++,fortran --with-cpu=generic --build=x86_64-redhat-linux
> Thread model: posix
> gcc version 4.4.0 (GCC)
>
This is a common case handled by patch in
http://gcc.gnu.org/ml/gcc-patches/2010-04/msg00706.html
--
davidxl at gcc dot gnu dot org changed:
What |Removed |Added
----------------------------------------------------------------------------
CC| |davidxl at gcc dot gnu dot
| |org
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42643
^ permalink raw reply [flat|nested] 3+ messages in thread
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Thread overview: 3+ messages (download: mbox.gz / follow: Atom feed)
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[not found] <bug-42643-4@http.gcc.gnu.org/bugzilla/>
2012-01-06 20:09 ` [Bug c/42643] "may be used uninitialized" compiled with "-Wall -O" mi+gcc at aldan dot algebra.com
2012-12-28 21:27 ` steven at gcc dot gnu.org
2010-01-07 0:48 [Bug c/42643] New: " numidee at synopsys dot com
2010-04-21 0:29 ` [Bug c/42643] " davidxl at gcc dot gnu dot org
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