[Bug c++/51545] New: missing -Wparentheses diagnostic with compound assignment used as condition

[Bug c++/51545] New: missing -Wparentheses diagnostic with compound assignment used as condition

[manu at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51545

             Bug #: 51545
           Summary: missing -Wparentheses diagnostic  with compound
                    assignment used as condition
    Classification: Unclassified
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: manu@gcc.gnu.org


Noticed here:
http://llvm.org/devmtg/2011-11/Weber_Wennborg_UsingClangInChromium.pdf

Testcase:

int foo(int x, int y)
{
  if (x|=y) return 0;
  return 1;
}

gcc 4.7 -Wall -Wextra -Wparentheses -Wlogical-op -Wtype-limits prints nothing.

clang 3.0 without extra flags:

test.cc:3:8: warning: using the result of an assignment as a condition without
parentheses [-Wparentheses]
  if (x|=y) return 0;
      ~^~~
test.cc:3:8: note: place parentheses around the assignment to silence this
warning                           
  if (x|=y) return 0;
       ^
      (   )
test.cc:3:8: note: use '!=' to turn this compound assignment into an inequality
comparison
  if (x|=y) return 0;
       ^~
       !=
1 warning generated.


Nonetheless, I still believe that using extra parentheses to silence these
warnings actually hides bugs and there are better alternatives. See PR25733.

[Bug c++/51545] missing -Wparentheses diagnostic with compound assignment used as condition

[marc.glisse at normalesup dot org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51545

Marc Glisse <marc.glisse at normalesup dot org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |marc.glisse at normalesup
                   |                            |dot org

--- Comment #1 from Marc Glisse <marc.glisse at normalesup dot org> 2011-12-14 22:27:15 UTC ---
PR 44949?

[Bug c++/51545] missing -Wparentheses diagnostic with compound assignment used as condition

[mikpe at it dot uu.se]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51545

--- Comment #2 from Mikael Pettersson <mikpe at it dot uu.se> 2011-12-15 12:09:21 UTC ---
Or perhaps PR50012?  Parenthesized expressions get TREE_NO_WARNING set on them.

[Bug c++/51545] missing -Wparentheses diagnostic with compound assignment used as condition

[egallager at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51545

Eric Gallager <egallager at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |egallager at gcc dot gnu.org,
                   |                            |msebor at gcc dot gnu.org

--- Comment #4 from Eric Gallager <egallager at gcc dot gnu.org> ---
(In reply to Mikael Pettersson from comment #2)
> Or perhaps PR50012?  Parenthesized expressions get TREE_NO_WARNING set on
> them.

I wonder if Martin Sebor's reworking of TREE_NO_WARNING has any effect here?

[Bug c++/51545] missing -Wparentheses diagnostic with compound assignment used as condition

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=51545

Martin Sebor <msebor at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
      Known to fail|                            |11.2.0, 12.0, 4.1.0
   Last reconfirmed|2017-08-18 00:00:00         |2021-8-13
            Version|unknown                     |4.0.0

--- Comment #5 from Martin Sebor <msebor at gcc dot gnu.org> ---
No change in 12.0.