Re: Warning about -Wmain for local variables

Re: Warning about -Wmain for local variables

[Prathamesh Kulkarni]

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On 30 May 2018 at 18:12, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
> On 30 May 2018 at 11:40, Prathamesh Kulkarni wrote:
>> gcc with -Wmain warns for local variables named main.
>>
>> int foo()
>> {
>>   int main = 0;
>>   return main;
>> }
>>
>> a.c: In function ‘foo’:
>> a.c:3:7: warning: ‘main’ is usually a function [-Wmain]
>>    int main = 1;
>>        ^~~~
>>
>> Is this intended ? I assumed that the warning's intent was for
>> diagnosing variable named main having only external linkage.
>
> It was added more than 20 years ago by https://gcc.gnu.org/r13517 and
> looks like it has always worked as it does now, without considering
> linkage.
>
> Only warning for entities with external linkage seems reasonable to
> me, but that would be for the C front-end or diagnostics maintainers
> to decide.
Thanks for the suggestions. I have attached (untested) patch that warns
for Wmain if TREE_PUBLIC (decl) is true.
Does it look OK ?

Thanks,
Prathamesh

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2018-05-30  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>

	* c/c-decl.c (start_decl): Add check TREE_PUBLIC (decl) for -Wmain.

testsuite/
	* gcc.dg/wmain.c: New.

diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 3c4b18edf56..c5311741629 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -4700,7 +4700,8 @@ start_decl (struct c_declarator *declarator, struct c_declspecs *declspecs,
   if (expr)
     add_stmt (fold_convert (void_type_node, expr));
 
-  if (TREE_CODE (decl) != FUNCTION_DECL && MAIN_NAME_P (DECL_NAME (decl)))
+  if (TREE_CODE (decl) != FUNCTION_DECL && MAIN_NAME_P (DECL_NAME (decl))
+      && TREE_PUBLIC (decl))
     warning (OPT_Wmain, "%q+D is usually a function", decl);
 
   if (initialized)
diff --git a/gcc/testsuite/gcc.dg/wmain.c b/gcc/testsuite/gcc.dg/wmain.c
new file mode 100644
index 00000000000..06fc26fd398
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/wmain.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-Wall" } */
+
+int main; /* { dg-warning "'main' is usually a function" } */
+
+int foo()
+{
+  int main = 1; /* { dg-bogus "'main' is usually a function" } */
+  return main;
+}

Re: Warning about -Wmain for local variables

[Prathamesh Kulkarni]

On 30 May 2018 at 21:21, Prathamesh Kulkarni
<prathamesh.kulkarni@linaro.org> wrote:
> On 30 May 2018 at 18:12, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
>> On 30 May 2018 at 11:40, Prathamesh Kulkarni wrote:
>>> gcc with -Wmain warns for local variables named main.
>>>
>>> int foo()
>>> {
>>>   int main = 0;
>>>   return main;
>>> }
>>>
>>> a.c: In function ‘foo’:
>>> a.c:3:7: warning: ‘main’ is usually a function [-Wmain]
>>>    int main = 1;
>>>        ^~~~
>>>
>>> Is this intended ? I assumed that the warning's intent was for
>>> diagnosing variable named main having only external linkage.
>>
>> It was added more than 20 years ago by https://gcc.gnu.org/r13517 and
>> looks like it has always worked as it does now, without considering
>> linkage.
>>
>> Only warning for entities with external linkage seems reasonable to
>> me, but that would be for the C front-end or diagnostics maintainers
>> to decide.
> Thanks for the suggestions. I have attached (untested) patch that warns
> for Wmain if TREE_PUBLIC (decl) is true.
> Does it look OK ?
ping https://gcc.gnu.org/ml/gcc-patches/2018-05/msg01739.html

Thanks,
Prathamesh
>
> Thanks,
> Prathamesh

Re: Warning about -Wmain for local variables

[Jeff Law]

On 05/30/2018 09:51 AM, Prathamesh Kulkarni wrote:
> On 30 May 2018 at 18:12, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
>> On 30 May 2018 at 11:40, Prathamesh Kulkarni wrote:
>>> gcc with -Wmain warns for local variables named main.
>>>
>>> int foo()
>>> {
>>>   int main = 0;
>>>   return main;
>>> }
>>>
>>> a.c: In function ‘foo’:
>>> a.c:3:7: warning: ‘main’ is usually a function [-Wmain]
>>>    int main = 1;
>>>        ^~~~
>>>
>>> Is this intended ? I assumed that the warning's intent was for
>>> diagnosing variable named main having only external linkage.
>> It was added more than 20 years ago by https://gcc.gnu.org/r13517 and
>> looks like it has always worked as it does now, without considering
>> linkage.
>>
>> Only warning for entities with external linkage seems reasonable to
>> me, but that would be for the C front-end or diagnostics maintainers
>> to decide.
> Thanks for the suggestions. I have attached (untested) patch that warns
> for Wmain if TREE_PUBLIC (decl) is true.
> Does it look OK ?
> 
> Thanks,
> Prathamesh
> 
> 
> wmain-1.txt
> 
> 
> 2018-05-30  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>
> 
> 	* c/c-decl.c (start_decl): Add check TREE_PUBLIC (decl) for -Wmain.
> 
> testsuite/
> 	* gcc.dg/wmain.c: New.
After the usual testing, this is OK.

jeff

Re: Warning about -Wmain for local variables

[Prathamesh Kulkarni]

On 28 June 2018 at 08:46, Jeff Law <law@redhat.com> wrote:
> On 05/30/2018 09:51 AM, Prathamesh Kulkarni wrote:
>> On 30 May 2018 at 18:12, Jonathan Wakely <jwakely.gcc@gmail.com> wrote:
>>> On 30 May 2018 at 11:40, Prathamesh Kulkarni wrote:
>>>> gcc with -Wmain warns for local variables named main.
>>>>
>>>> int foo()
>>>> {
>>>>   int main = 0;
>>>>   return main;
>>>> }
>>>>
>>>> a.c: In function ‘foo’:
>>>> a.c:3:7: warning: ‘main’ is usually a function [-Wmain]
>>>>    int main = 1;
>>>>        ^~~~
>>>>
>>>> Is this intended ? I assumed that the warning's intent was for
>>>> diagnosing variable named main having only external linkage.
>>> It was added more than 20 years ago by https://gcc.gnu.org/r13517 and
>>> looks like it has always worked as it does now, without considering
>>> linkage.
>>>
>>> Only warning for entities with external linkage seems reasonable to
>>> me, but that would be for the C front-end or diagnostics maintainers
>>> to decide.
>> Thanks for the suggestions. I have attached (untested) patch that warns
>> for Wmain if TREE_PUBLIC (decl) is true.
>> Does it look OK ?
>>
>> Thanks,
>> Prathamesh
>>
>>
>> wmain-1.txt
>>
>>
>> 2018-05-30  Prathamesh Kulkarni  <prathamesh.kulkarni@linaro.org>
>>
>>       * c/c-decl.c (start_decl): Add check TREE_PUBLIC (decl) for -Wmain.
>>
>> testsuite/
>>       * gcc.dg/wmain.c: New.
> After the usual testing, this is OK.
Sorry for late response. I committed the patch after bootstrap+test on x86_64.

Regards,
Prathamesh
>
> jeff