[Bug c/87387] trunk/gcc/builtins.c:585:7: warning: -Wself-assign problem

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87387

--- Comment #1 from David Binderman  ---
I found this bug by compiling gcc with the new clang 7.0

It seems that gcc can't be encouraged to warn about self-assignment.

For example:

$cat sep23a.cc
// -Wself-assign. clang has it. gcc doesn't.

extern void g( int);

void f(int n)
{
int m = 2 * n;

m = m;

g( m);
}

$ ~/gcc/results/bin/gcc -c -O2 -Wall -Wextra sep23a.cc
$ 

Given that this warning finds bugs in gcc itself, would this
-Wself-assign warning be worth implementing in gcc ?

I'll have a go at compiling the rest of the world with clang-7.0
and see what it finds.

[Bug c/87387] trunk/gcc/builtins.c:585:7: warning: -Wself-assign problem

[dcb314 at hotmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87387

--- Comment #2 from David Binderman  ---
Looks like an old implementation:

https://gcc.gnu.org/ml/gcc-patches/2010-06/msg02390.html

It might be worth using this as a starting point.

[Bug c/87387] trunk/gcc/builtins.c:585:7: warning: -Wself-assign problem

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87387

Eric Gallager  changed:

   What|Removed |Added

 CC||egallager at gcc dot gnu.org
   See Also||https://gcc.gnu.org/bugzill
   ||a/show_bug.cgi?id=53129

--- Comment #3 from Eric Gallager  ---
(In reply to David Binderman from comment #1)
> I found this bug by compiling gcc with the new clang 7.0
> 
> It seems that gcc can't be encouraged to warn about self-assignment.
> 
> For example:
> 
> $cat sep23a.cc
> // -Wself-assign. clang has it. gcc doesn't.
> 
> extern void g( int);
> 
> void f(int n)
> {
>   int m = 2 * n;
> 
>   m = m;
> 
>   g( m);
> }
> 
> $ ~/gcc/results/bin/gcc -c -O2 -Wall -Wextra sep23a.cc
> $ 
> 
> Given that this warning finds bugs in gcc itself, would this
> -Wself-assign warning be worth implementing in gcc ?

That's bug 53129.

> 
> I'll have a go at compiling the rest of the world with clang-7.0
> and see what it finds.

[Bug c/87387] trunk/gcc/builtins.c:585:7: warning: -Wself-assign problem

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87387

--- Comment #4 from Jeffrey A. Law  ---
Author: law
Date: Tue Sep 25 22:17:45 2018
New Revision: 264585

URL: https://gcc.gnu.org/viewcvs?rev=264585&root=gcc&view=rev
Log:
PR c/87387
* builtins.c (unterminated_array): Simplify.
* expr.c (string_constant): Handle SSA_NAME.  Add more exceptions
where pointer arithmetic is safe.

* gcc.dg/warn-stpcpy-no-nul.c: Drop unnecessary xfails.
* gcc.dg/warn-stplen-no-nul.c: Likewise.

Modified:
trunk/gcc/ChangeLog
trunk/gcc/builtins.c
trunk/gcc/expr.c
trunk/gcc/testsuite/ChangeLog
trunk/gcc/testsuite/gcc.dg/warn-stpcpy-no-nul.c
trunk/gcc/testsuite/gcc.dg/warn-strlen-no-nul.c

[Bug c/87387] trunk/gcc/builtins.c:585:7: warning: -Wself-assign problem

[law at redhat dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87387

Jeffrey A. Law  changed:

   What|Removed |Added

 Status|UNCONFIRMED |RESOLVED
 Resolution|--- |FIXED

--- Comment #5 from Jeffrey A. Law  ---
Fixed on the trunk.

[Bug c/87387] trunk/gcc/builtins.c:585:7: warning: -Wself-assign problem

[jamespharvey20 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87387

--- Comment #6 from jamespharvey20 at gmail dot com ---
This fix introduces bug 87672.