[Bug c++/25181] New: wrong "will never be executed" warning in switch - case block

[Bug c++/25181] New: wrong "will never be executed" warning in switch - case block

[oliverst at online dot de]

The following code will report this:

C:\Dev-Cpp\Projects\test-stlport\main_18.cpp In function `int test_18()': 
13 C:\Dev-Cpp\Projects\test-stlport\main_18.cpp [Warning] will never be
executed 

extern int abort();

int test_18()
{
        int type;
        switch (type)
        {
        case 1:
                int ret = abort();
                if (ret != 0)
                        return 2;

                break;

        case 3:
                break;

        default:                        
                return 1;
        }

        return 0;
}
If you remove "case 3" or "default" the warning will go away.

I already reported something similar under bug 24968.

C:\MinGW_3.4.4\bin>gcc -v
Reading specs from ../lib/gcc/mingw32/3.4.4/specs
Configured with: ../gcc/configure --with-gcc --with-gnu-ld --with-gnu-as
--host=
mingw32 --target=mingw32 --prefix=/mingw --enable-threads --disable-nls
--enable
-languages=c,c++,f77,ada,objc,java --disable-win32-registry --disable-shared
--e
nable-sjlj-exceptions --enable-libgcj --disable-java-awt --without-x
--enable-ja
va-gc=boehm --disable-libgcj-debug --enable-interpreter
--enable-hash-synchroniz
ation --enable-libstdcxx-debug
Thread model: win32
gcc version 3.4.4 (mingw special)


-- 
           Summary: wrong "will never be executed" warning in switch - case
                    block
           Product: gcc
           Version: 3.4.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: oliverst at online dot de


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25181

[Bug c++/25181] wrong "will never be executed" warning in switch - case block

[pinskia at gcc dot gnu dot org]

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------- Comment #1 from pinskia at gcc dot gnu dot org  2005-11-30 16:08 -------
This is invalid code:
t.cc: In function ‘int test_18()’:
t.cc:15: error: jump to case label
t.cc:9: error:   crosses initialization of ‘int ret’
t.cc:18: error: jump to case label
t.cc:9: error:   crosses initialization of ‘int ret’

We should reject this.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25181

[Bug c++/25181] [3.4 Regression] wrong "will never be executed" warning in switch - case block

[pinskia at gcc dot gnu dot org]

------- Comment #2 from pinskia at gcc dot gnu dot org  2005-11-30 16:11 -------
(In reply to comment #1)
> We should reject this.
But that is a different bug.
Anyways fixing up the code to be legal code:
extern int abort();

int test_18()
{
        int type;
        switch (type)
        {
        case 1:
 {               int ret = abort();
                if (ret != 0)
                        return 2;

                break;}

        case 3:
                break;

        default:
                return 1;
        }

        return 0;
}
---

We only warn for 3.4.x and below except 3.0.4 works so this is only a 3.4
regression.


-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
           Keywords|                            |diagnostic
      Known to fail|                            |3.3.3 3.4.0
      Known to work|                            |3.0.4 4.0.0 4.1.0 4.2.0
   Last reconfirmed|0000-00-00 00:00:00         |2005-11-30 16:11:44
               date|                            |
            Summary|wrong "will never be        |[3.4 Regression] wrong "will
                   |executed" warning in switch |never be executed" warning
                   |- case block                |in switch - case block
   Target Milestone|---                         |3.4.6


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25181

[Bug c++/25181] [3.4 Regression] wrong "will never be executed" warning in switch - case block

[oliverst at online dot de]

------- Comment #3 from oliverst at online dot de  2005-11-30 20:38 -------
I forgot to meintion, that this happens with C and C++, so I guess it's a
middle-end bug!?


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25181

[Bug middle-end/25181] [3.4 Regression] wrong "will never be executed" warning in switch - case block

[gdr at integrable-solutions dot net]

------- Comment #4 from gdr at integrable-solutions dot net  2005-11-30 22:23 -------
Subject: Re:  [3.4 Regression] wrong "will never be executed" warning in switch
- case block

"oliverst at online dot de" <gcc-bugzilla@gcc.gnu.org> writes:

| I forgot to meintion, that this happens with C and C++, so I guess it's a
| middle-end bug!?

Most probably.

-- Gaby


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25181

[Bug middle-end/25181] [3.4 Regression] wrong "will never be executed" warning in switch - case block

[oliverst at online dot de]

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------- Comment #5 from oliverst at online dot de  2005-12-01 12:32 -------
(In reply to comment #1)
> This is invalid code:
> t.cc: In function ‘int test_18()’:
> t.cc:15: error: jump to case label
> t.cc:9: error:   crosses initialization of ‘int ret’
> t.cc:18: error: jump to case label
> t.cc:9: error:   crosses initialization of ‘int ret’
> 
> We should reject this.
> 

Will you create a bug report for this or is there already one filed?

I just tried it with GCC 4.0.2 (downloaded it from
http://www.thisiscool.com/gcc_mingw.htm) and the code is still accepted.

C:\MinGW_4.0.2\bin>gcc -v
Using built-in specs.
Target: i686-pc-mingw32
Configured with: /datal/gcc/gcc/configure --prefix=/datal/gcc/build/wingcc
--bui
ld=i686-pc-linux-gnu --host=i686-pc-mingw32 --target=i686-pc-mingw32
--enable-la
nguages=c,c++,java --with-gcc --with-gnu-as --with-gnu-ld
--with-as=/datal/gcc/b
uild/crossgcc/bin/i686-pc-mingw32-as
--with-ld=/datal/gcc/build/crossgcc/bin/i68
6-pc-mingw32-ld --enable-threads=win32 --disable-nls --disable-win32-registry
--
disable-shared --disable-debug --without-newlib --enable-libgcj
--disable-java-a
wt --without-x --enable-java-gc=boehm --disable-libgcj-debug
--enable-interprete
r --enable-hash-synchronization --enable-sjlj-exceptions
--enable-libgcj-multifi
le --enable-libgcj-mingw-osapi=ansi
Thread model: win32
gcc version 4.0.2


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25181

[Bug middle-end/25181] [3.4 Regression] wrong "will never be executed" warning in switch - case block

[gdr at gcc dot gnu dot org]

------- Comment #6 from gdr at gcc dot gnu dot org  2006-03-01 05:01 -------
Fixed in 4.0.0 and up.


-- 

gdr at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|3.4.6                       |4.0.0


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25181