[Bug c++/37070] bogus unreachable warning on throw statement

[bangerth at dealii dot org]

--- Comment #5 from bangerth at dealii dot org  2008-08-13 16:27 ---
Confirmed. What I believe Andrew was pointing out are the internal reasons
why this warning happens. However, the warning is clearly bogus, the flag
-Wunreachable-code isn't useful if it warns on this sort of code.

W.


-- 

bangerth at dealii dot org changed:

   What|Removed |Added

 CC||bangerth at dealii dot org
 Status|UNCONFIRMED |NEW
 Ever Confirmed|0   |1
   Last reconfirmed|-00-00 00:00:00 |2008-08-13 16:27:54
   date||


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37070

[Bug c++/37070] bogus unreachable warning on throw statement

[pinskia at gcc dot gnu dot org]

--- Comment #1 from pinskia at gcc dot gnu dot org  2008-08-09 22:31 ---
I don't think this is really bogus as the expression inside a throw cannot
throw so GCC is able to optimize away the catch inside that throw.
  [t.cc : 3] try
{
  [t.cc : 3] D.2413 = (int *) D.2410;
  [t.cc : 3] *D.2413 = 0;
}
  catch
{
  [t.cc : 3] eh_filter (NULL)
{

[t.cc : 3] terminate ();

}
}

That catch is not reachable.


-- 

pinskia at gcc dot gnu dot org changed:

   What|Removed |Added

   Severity|normal  |enhancement


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37070

[Bug c++/37070] bogus unreachable warning on throw statement

[sebor at roguewave dot com]

--- Comment #2 from sebor at roguewave dot com  2008-08-09 22:51 ---
I'm not sure what you're trying to say but it sure looks like a bug to me.
How else is one supposed to throw an exception without triggering this
warning?

Btw., the argument of a throw expression can throw, and when it does, it
becomes the thrown object:

$ cat t.C  g++ -O2 -Wunreachable-code t.C  ./a.out; echo $?
struct S { S () { throw 0; } };
void bar () { throw S (); }

int main ()
{
try { bar (); }
catch (int) { return 0; }
return 1;
}
t.C: In constructor ‘S::S()’:
t.C:1: warning: will never be executed
t.C: In function ‘void bar()’:
t.C:2: warning: will never be executed
0


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37070

[Bug c++/37070] bogus unreachable warning on throw statement

[pinskia at gcc dot gnu dot org]

--- Comment #3 from pinskia at gcc dot gnu dot org  2008-08-09 22:59 ---
 t.C: In function ‘void bar()’:
 t.C:2: warning: will never be executed

I don't get that warning in either the trunk or in 4.0.1.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37070

[Bug c++/37070] bogus unreachable warning on throw statement

[sebor at roguewave dot com]

--- Comment #4 from sebor at roguewave dot com  2008-08-10 02:23 ---
My gcc is yesterday's build:
gcc version 4.4.0 20080808 (experimental) (GCC) 


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37070