[Bug c/21750] New: GCC gives may be used uninitialized warning for a non-conditional initialised variable. (not a duplicate bug!)

[Bug c/21750] New: GCC gives may be used uninitialized warning for a non-conditional initialised variable. (not a duplicate bug!)

[j dot w dot r dot degoede at hhs dot nl]

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I'm using Fedora Rawhide tree (FC4 develtree) the gcc rpm version is:
---
[hans@cq229 ~]$ rpm -q gcc
gcc-4.0.0-8
---

Gcc-version:
---
Using built-in specs.
Target: i386-redhat-linux
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --enable-shared --enable-threads=posix
--enable-checking=release --with-system-zlib --enable-__cxa_atexit
--disable-libunwind-exceptions --enable-libgcj-multifile
--enable-languages=c,c++,objc,java,f95,ada --enable-java-awt=gtk
--with-java-home=/usr/lib/jvm/java-1.4.2-gcj-1.4.2.0/jre --host=i386-redhat-linux
Thread model: posix
gcc version 4.0.0 20050519 (Red Hat 4.0.0-8)
---

Commandline triggering the bug:
---
gcc -o gglide.o -Wall -W -I. -I../../incsrc -I../../minihwc -I../../cinit
-I../../../swlibs/fxmisc -I../../../swlibs/newpci/pcilib
-I../../../swlibs/fxmemmap -I../../../swlibs/texus2/lib -D__linux__ -DDRI_BUILD
-DGLIDE3 -DGLIDE3_ALPHA -DGLIDE_HW_TRI_SETUP=1 -DGLIDE_INIT_HWC
-DGLIDE_PACKED_RGB=0 -DGLIDE_PACKET3_TRI_SETUP=1 -DGLIDE_TRI_CULLING=1
-DUSE_PACKET_FIFO=1 -DH3 -DFX_GLIDE_H5_CSIM=1 -DFX_GLIDE_NAPALM=1 -DGLIDE_PLUG
-DGLIDE_SPLASH -DHAVE_TEXUS2 -DGL_AMD3D -DGL_MMX -DGL_SSE -DGL_SSE2 -DGL_X86 -O2
-g -pipe -Wp,-D_FORTIFY_SOURCE=2 -fexceptions -m32 -march=i386 -mtune=pentium4
-fasynchronous-unwind-tables -Wno-unused-parameter -save-temps -c gglide.c
---

Compiling gglide.c with the above cmdline results in the following warnings:
---
gglide.c: In function ‘_grBufferClear2D’:
gglide.c:957: warning: ‘clip0min’ may be used uninitialized in this function
gglide.c:964: warning: ‘height’ may be used uninitialized in this function
gglide.c:964: warning: ‘width’ may be used uninitialized in this function
gglide.c:957: warning: ‘command’ may be used uninitialized in this function
---

I've attached an .i file as instructed. line 957 => 7312 in the .i file.

Notice that command, width and height get initialised unconditional before use.
(the offsetoff use is use of a member of a struct with the same name not of the
variable).


I've seen this same bug in another file too. The strange thing is that moving
the "do { } while(0);" which contains "*_regGroupFifoPtr++ = ((height << 16) |
width);" up a bit to line 7404, which moves it over a block which doesn't touch
width or height makes the warning for width and height go away.

I've seen the same thing in the other file moving the code using the var up over
a (big) block which doesn't touch the var in any way makes the warning go away.
It is as if gcc forgets that the var has been initialised if it isn't used for a
number of lines.

-- 
           Summary: GCC gives may be used uninitialized warning for a non-
                    conditional initialised variable. (not a duplicate bug!)
           Product: gcc
           Version: 4.0.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: j dot w dot r dot degoede at hhs dot nl
                CC: gcc-bugs at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21750

[Bug c/21750] GCC gives may be used uninitialized warning for a non-conditional initialised variable. (not a duplicate bug!)

[j dot w dot r dot degoede at hhs dot nl]

------- Additional Comments From j dot w dot r dot degoede at hhs dot nl  2005-05-25 12:57 -------
Created an attachment (id=8965)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=8965&action=view)
File causing problem


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21750

[Bug middle-end/21750] GCC gives may be used uninitialized warning for a non-conditional initialised variable. (not a duplicate bug!)

[pinskia at gcc dot gnu dot org]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
          Component|c                           |middle-end
           Keywords|                            |diagnostic


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21750

[Bug middle-end/21750] GCC gives may be used uninitialized warning for a non-conditional initialised variable. (not a duplicate bug!)

[James dot Juran at baesystems dot com]

-- 
           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |James dot Juran at
                   |                            |baesystems dot com


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21750

[Bug middle-end/21750] GCC gives may be used uninitialized warning for a non-conditional initialised variable. (not a duplicate bug!)

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2005-11-26 16:39 -------
We have:
 if (gc->contextP) { 
...
set hieght
set width
set clip0min
set command
...
}
...
if (xxxxxx) {....}
...
if (gc->contextP) {
...
use clipOmin
use command
use hieght
use width
use clip0min
...
}

Anyways this is a dup of bug 5035

*** This bug has been marked as a duplicate of 5035 ***


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |DUPLICATE


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21750

[Bug middle-end/21750] GCC gives may be used uninitialized warning for a non-conditional initialised variable. (not a duplicate bug!)

[gdr at gcc dot gnu dot org]

-- 

gdr at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2005-11-26 07:40:34
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21750