Re: reject decl with incomplete struct/union type in check_global_declaration()

[Marek Polacek]

On Wed, Jan 20, 2016 at 06:52:48PM +0530, Prathamesh Kulkarni wrote:
> Thanks for the review, I have done the suggested changes in this
> version of the patch.
> Ok for trunk ?

Given that Joseph already approved substance of the patch, this is ok
(but you might want to correct a typo below), thanks.

> +/* We need to walk over decls with incomplete struct/union/enum types
> +   after parsing the whole translation unit.
> +   In finish_decl(), if the decl is static, has incomplete
> +   struct/union/enum type, it is appened to incomplete_record_decls.

"appended"

> +   In c_parser_translation_unit(), we iterate over incomplete_record_decls
> +   and report error if any of the decls are still incomplete.  */ 

Marek

Re: reject decl with incomplete struct/union type in check_global_declaration()

[Prathamesh Kulkarni]

On 19 January 2016 at 16:49, Marek Polacek  wrote:
> Sorry for speaking up late, but I think we could do better with formatting
> in this patch:
>
> On Sat, Jan 16, 2016 at 03:45:22PM +0530, Prathamesh Kulkarni wrote:
>> diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
>> index 915376d..d36fc67 100644
>> --- a/gcc/c/c-decl.c
>> +++ b/gcc/c/c-decl.c
>> @@ -4791,6 +4791,13 @@ finish_decl (tree decl, location_t init_loc, tree 
>> init,
>>  TREE_TYPE (decl) = error_mark_node;
>>}
>>
>> +  if ((RECORD_OR_UNION_TYPE_P (TREE_TYPE (decl))
>> +   || TREE_CODE (TREE_TYPE (decl)) == ENUMERAL_TYPE)
>> +   && DECL_SIZE (decl) == 0 && TREE_STATIC (decl))
>
> DECL_SIZE yields a tree, so I'd rather see NULL_TREE instead of 0 here (yeah,
> the enclosing code uses 0s :().  The "&& TREE_STATIC..." should be on its own
> line.
>
>> + {
>> +   incomplete_record_decls.safe_push (decl);
>> + }
>> +
>
> Redundant braces.
>
>> diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
>> index a0e0052..3c8a496 100644
>> --- a/gcc/c/c-parser.c
>> +++ b/gcc/c/c-parser.c
>> @@ -59,6 +59,8 @@ along with GCC; see the file COPYING3.  If not see
>>  #include "gimple-expr.h"
>>  #include "context.h"
>>
>> +vec incomplete_record_decls = vNULL;
>
> This could use a comment.
>
>> +
>> +  for (unsigned i = 0; i < incomplete_record_decls.length (); ++i)
>> +{
>> +  tree decl = incomplete_record_decls[i];
>> +  if (DECL_SIZE (decl) == 0 && TREE_TYPE (decl) != error_mark_node)
>
> I'd s/0/NULL_TREE/.
Thanks for the review, I have done the suggested changes in this
version of the patch.
Ok for trunk ?

Thanks,
Prathamesh
>
> Marek
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 5830e22..1ec6042 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -4791,6 +4791,12 @@ finish_decl (tree decl, location_t init_loc, tree init,
   TREE_TYPE (decl) = error_mark_node;
 }
 
+  if ((RECORD_OR_UNION_TYPE_P (TREE_TYPE (decl))
+ || TREE_CODE (TREE_TYPE (decl)) == ENUMERAL_TYPE)
+ && DECL_SIZE (decl) == NULL_TREE
+ && TREE_STATIC (decl))
+   incomplete_record_decls.safe_push (decl);
+
   if (is_global_var (decl) && DECL_SIZE (decl) != 0)
{
  if (TREE_CODE (DECL_SIZE (decl)) == INTEGER_CST)
diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index 919680a..1d3b9e1 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -59,6 +59,15 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimple-expr.h"
 #include "context.h"
 
+/* We need to walk over decls with incomplete struct/union/enum types
+   after parsing the whole translation unit.
+   In finish_decl(), if the decl is static, has incomplete
+   struct/union/enum type, it is appened to incomplete_record_decls.
+   In c_parser_translation_unit(), we iterate over incomplete_record_decls
+   and report error if any of the decls are still incomplete.  */ 
+
+vec incomplete_record_decls = vNULL;
+
 void
 set_c_expr_source_range (c_expr *expr,
 location_t start, location_t finish)
@@ -1421,6 +1430,16 @@ c_parser_translation_unit (c_parser *parser)
}
   while (c_parser_next_token_is_not (parser, CPP_EOF));
 }
+
+  for (unsigned i = 0; i < incomplete_record_decls.length (); ++i)
+{
+  tree decl = incomplete_record_decls[i];
+  if (DECL_SIZE (decl) == NULL_TREE && TREE_TYPE (decl) != error_mark_node)
+   {
+ error ("storage size of %q+D isn%'t known", decl);
+ TREE_TYPE (decl) = error_mark_node;
+   }
+}
 }
 
 /* Parse an external declaration (C90 6.7, C99 6.9).
diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h
index 81a3d58..cf79ba7 100644
--- a/gcc/c/c-tree.h
+++ b/gcc/c/c-tree.h
@@ -731,4 +731,6 @@ set_c_expr_source_range (c_expr *expr,
 /* In c-fold.c */
 extern tree decl_constant_value_for_optimization (tree);
 
+extern vec incomplete_record_decls;
+
 #endif /* ! GCC_C_TREE_H */
diff --git a/gcc/testsuite/gcc.dg/Wcxx-compat-8.c 
b/gcc/testsuite/gcc.dg/Wcxx-compat-8.c
index f7e8c55..4e9ddc1 100644
--- a/gcc/testsuite/gcc.dg/Wcxx-compat-8.c
+++ b/gcc/testsuite/gcc.dg/Wcxx-compat-8.c
@@ -33,6 +33,7 @@ enum e3
 
 __typeof__ (struct s5 { int i; }) v5; /* { dg-warning "invalid in C\[+\]\[+\]" 
} */
 __typeof__ (struct t5) w5; /* { dg-bogus "invalid in C\[+\]\[+\]" } */
+  /* { dg-error "storage size of 'w5' isn't known" "" { target *-*-* } 35 } */
 
 int
 f1 (struct s1 *p)
@@ -64,4 +65,4 @@ f5 ()
   return &((struct t8) { });  /* { dg-warning "invalid in C\[+\]\[+\]" } */
 }
 
-/* { dg-error "invalid use of undefined type" "" { target *-*-* } 64 } */
+/* { dg-error "invalid use of undefined type" "" { target *-*-* } 65 } */
diff --git a/gcc/testsuite/gcc.dg/declspec-1.c 
b/gcc/testsuite/gcc.dg/declspec-1.c
index c19f107..b024601 100644
--- a/gcc/testsuite/gcc.dg/declspec-1.c
+++ b/gcc/testsuite/gcc.dg/declspec-1.c
@@ -9,13 +9,15 @@ typedef int t;
 /* These should all be diagnosed, but only once, not 

Re: reject decl with incomplete struct/union type in check_global_declaration()

[Marek Polacek]

Sorry for speaking up late, but I think we could do better with formatting
in this patch:

On Sat, Jan 16, 2016 at 03:45:22PM +0530, Prathamesh Kulkarni wrote:
> diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
> index 915376d..d36fc67 100644
> --- a/gcc/c/c-decl.c
> +++ b/gcc/c/c-decl.c
> @@ -4791,6 +4791,13 @@ finish_decl (tree decl, location_t init_loc, tree init,
>  TREE_TYPE (decl) = error_mark_node;
>}
>  
> +  if ((RECORD_OR_UNION_TYPE_P (TREE_TYPE (decl))
> +   || TREE_CODE (TREE_TYPE (decl)) == ENUMERAL_TYPE)
> +   && DECL_SIZE (decl) == 0 && TREE_STATIC (decl))

DECL_SIZE yields a tree, so I'd rather see NULL_TREE instead of 0 here (yeah,
the enclosing code uses 0s :().  The "&& TREE_STATIC..." should be on its own
line.

> + {
> +   incomplete_record_decls.safe_push (decl);
> + }
> +

Redundant braces.

> diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
> index a0e0052..3c8a496 100644
> --- a/gcc/c/c-parser.c
> +++ b/gcc/c/c-parser.c
> @@ -59,6 +59,8 @@ along with GCC; see the file COPYING3.  If not see
>  #include "gimple-expr.h"
>  #include "context.h"
>  
> +vec incomplete_record_decls = vNULL;

This could use a comment.

> +
> +  for (unsigned i = 0; i < incomplete_record_decls.length (); ++i)
> +{
> +  tree decl = incomplete_record_decls[i];
> +  if (DECL_SIZE (decl) == 0 && TREE_TYPE (decl) != error_mark_node)

I'd s/0/NULL_TREE/.

Marek

Re: reject decl with incomplete struct/union type in check_global_declaration()

[Joseph Myers]

On Sat, 16 Jan 2016, Prathamesh Kulkarni wrote:

> > There's a GNU C extension allowing forward declarations of enums, and it
> > seems that
> >
> > static enum e x;
> >
> > doesn't get diagnosed either with -fsyntax-only.  Thus I think you should
> > cover that case as well.
> Done in the attached patch. It regresses pr63549.c because the error
> showed up there, adjusted
> the test-case to accept the error.
> OK to commit ?

OK.

-- 
Joseph S. Myers
jos...@codesourcery.com

Re: reject decl with incomplete struct/union type in check_global_declaration()

[Prathamesh Kulkarni]

On 16 January 2016 at 02:56, Joseph Myers  wrote:
> On Fri, 15 Jan 2016, Prathamesh Kulkarni wrote:
>
>> On 15 January 2016 at 03:27, Joseph Myers  wrote:
>> > On Thu, 14 Jan 2016, Prathamesh Kulkarni wrote:
>> >
>> >> Hi,
>> >> For test-case containing only the following declaration:
>> >> static struct undefined_struct object;
>> >> gcc rejects it at -O0 in assemble_variable() with error "storage size
>> >> of  is unknown",
>> >> however no error is reported when compiled with -O2.
>> >
>> > Cf bug 24293 (for the -fsyntax-only case) - does this patch fix that?
>> Ah this doesn't fix PR24293, it seems analyze_function() doesn't get
>> called for -fsyntax-only.
>> I don't have a good solution for this. I assume varpool won't be
>> populated for -fsyntax-only ?
>> And we need to walk over decls with incomplete struct/union types
>> after parsing the whole translation unit.
>> In the attached patch, I kept a global vec incomplete_record_decls;
>> In finish_decl(), if the decl is static, has type struct/union and
>> size 0 then it is appened to incomplete_record_decls.
>> In c_parser_translation_unit(), iterate over incomplete_record_decls
>> and if report error if any decl has size zero.
>> The patch passes testsuite.
>
> There's a GNU C extension allowing forward declarations of enums, and it
> seems that
>
> static enum e x;
>
> doesn't get diagnosed either with -fsyntax-only.  Thus I think you should
> cover that case as well.
Done in the attached patch. It regresses pr63549.c because the error
showed up there, adjusted
the test-case to accept the error.
OK to commit ?

Thanks,
Prathamesh
>
> --
> Joseph S. Myers
> jos...@codesourcery.com
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 915376d..d36fc67 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -4791,6 +4791,13 @@ finish_decl (tree decl, location_t init_loc, tree init,
   TREE_TYPE (decl) = error_mark_node;
 }
 
+  if ((RECORD_OR_UNION_TYPE_P (TREE_TYPE (decl))
+ || TREE_CODE (TREE_TYPE (decl)) == ENUMERAL_TYPE)
+ && DECL_SIZE (decl) == 0 && TREE_STATIC (decl))
+   {
+ incomplete_record_decls.safe_push (decl);
+   }
+
   if (is_global_var (decl) && DECL_SIZE (decl) != 0)
{
  if (TREE_CODE (DECL_SIZE (decl)) == INTEGER_CST)
diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index a0e0052..3c8a496 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -59,6 +59,8 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimple-expr.h"
 #include "context.h"
 
+vec incomplete_record_decls = vNULL;
+
 void
 set_c_expr_source_range (c_expr *expr,
 location_t start, location_t finish)
@@ -1421,6 +1423,16 @@ c_parser_translation_unit (c_parser *parser)
}
   while (c_parser_next_token_is_not (parser, CPP_EOF));
 }
+
+  for (unsigned i = 0; i < incomplete_record_decls.length (); ++i)
+{
+  tree decl = incomplete_record_decls[i];
+  if (DECL_SIZE (decl) == 0 && TREE_TYPE (decl) != error_mark_node)
+   {
+ error ("storage size of %q+D isn%'t known", decl);
+ TREE_TYPE (decl) = error_mark_node;
+   }
+}
 }
 
 /* Parse an external declaration (C90 6.7, C99 6.9).
diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h
index 81a3d58..cf79ba7 100644
--- a/gcc/c/c-tree.h
+++ b/gcc/c/c-tree.h
@@ -731,4 +731,6 @@ set_c_expr_source_range (c_expr *expr,
 /* In c-fold.c */
 extern tree decl_constant_value_for_optimization (tree);
 
+extern vec incomplete_record_decls;
+
 #endif /* ! GCC_C_TREE_H */
diff --git a/gcc/testsuite/gcc.dg/Wcxx-compat-8.c 
b/gcc/testsuite/gcc.dg/Wcxx-compat-8.c
index f7e8c55..4e9ddc1 100644
--- a/gcc/testsuite/gcc.dg/Wcxx-compat-8.c
+++ b/gcc/testsuite/gcc.dg/Wcxx-compat-8.c
@@ -33,6 +33,7 @@ enum e3
 
 __typeof__ (struct s5 { int i; }) v5; /* { dg-warning "invalid in C\[+\]\[+\]" 
} */
 __typeof__ (struct t5) w5; /* { dg-bogus "invalid in C\[+\]\[+\]" } */
+  /* { dg-error "storage size of 'w5' isn't known" "" { target *-*-* } 35 } */
 
 int
 f1 (struct s1 *p)
@@ -64,4 +65,4 @@ f5 ()
   return &((struct t8) { });  /* { dg-warning "invalid in C\[+\]\[+\]" } */
 }
 
-/* { dg-error "invalid use of undefined type" "" { target *-*-* } 64 } */
+/* { dg-error "invalid use of undefined type" "" { target *-*-* } 65 } */
diff --git a/gcc/testsuite/gcc.dg/declspec-1.c 
b/gcc/testsuite/gcc.dg/declspec-1.c
index c19f107..b024601 100644
--- a/gcc/testsuite/gcc.dg/declspec-1.c
+++ b/gcc/testsuite/gcc.dg/declspec-1.c
@@ -9,13 +9,15 @@ typedef int t;
 /* These should all be diagnosed, but only once, not for every
identifier declared.  */
 struct s0 int x0, /* { dg-error "two or more data types" } */
-x1;
+/* { dg-error "storage size of 'x0' isn't known" "" { target *-*-* } 11 } */
+x1; /* { dg-error "storage size of 'x1' isn't known" } */ 
 
 char union u0 x2, /* { dg-error "two or more data types" } */
 x3;
 
 enum e0 struct s1 x4, /* { dg-error "two or 

Re: reject decl with incomplete struct/union type in check_global_declaration()

[Prathamesh Kulkarni]

On 15 January 2016 at 03:27, Joseph Myers  wrote:
> On Thu, 14 Jan 2016, Prathamesh Kulkarni wrote:
>
>> Hi,
>> For test-case containing only the following declaration:
>> static struct undefined_struct object;
>> gcc rejects it at -O0 in assemble_variable() with error "storage size
>> of  is unknown",
>> however no error is reported when compiled with -O2.
>
> Cf bug 24293 (for the -fsyntax-only case) - does this patch fix that?
Ah this doesn't fix PR24293, it seems analyze_function() doesn't get
called for -fsyntax-only.
I don't have a good solution for this. I assume varpool won't be
populated for -fsyntax-only ?
And we need to walk over decls with incomplete struct/union types
after parsing the whole translation unit.
In the attached patch, I kept a global vec incomplete_record_decls;
In finish_decl(), if the decl is static, has type struct/union and
size 0 then it is appened to incomplete_record_decls.
In c_parser_translation_unit(), iterate over incomplete_record_decls
and if report error if any decl has size zero.
The patch passes testsuite.

Thanks,
Prathamesh
>
>> g++ rejects it during parsing. I tried similarly in C FE by adding a
>> check for decl with incomplete struct/union type in finish_decl(),
>> however that fails to compile the following case:
>> typedef struct foo foo_t;
>> foo_t x;
>> struct foo { int i; };
>> g++ rejects the above case as well but gcc accepts it.
>> Do C and C++ standards differ in this regard ?
>
> I don't know about C++, but this sort of thing is valid C if the type is
> complete at the end of the translation unit or is an incomplete array type
> (but not in the case where the variable is static - such a case with
> static, if supported, is an extension).
>
> --
> Joseph S. Myers
> jos...@codesourcery.com
diff --git a/gcc/c/c-decl.c b/gcc/c/c-decl.c
index 915376d..ac542e1 100644
--- a/gcc/c/c-decl.c
+++ b/gcc/c/c-decl.c
@@ -4791,6 +4791,12 @@ finish_decl (tree decl, location_t init_loc, tree init,
   TREE_TYPE (decl) = error_mark_node;
 }
 
+  if (RECORD_OR_UNION_TYPE_P (TREE_TYPE (decl))
+ && DECL_SIZE (decl) == 0 && TREE_STATIC (decl)) 
+   {
+ incomplete_record_decls.safe_push (decl);
+   }
+
   if (is_global_var (decl) && DECL_SIZE (decl) != 0)
{
  if (TREE_CODE (DECL_SIZE (decl)) == INTEGER_CST)
diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.c
index a0e0052..8af04f7 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -59,6 +59,8 @@ along with GCC; see the file COPYING3.  If not see
 #include "gimple-expr.h"
 #include "context.h"
 
+vec incomplete_record_decls = vNULL;
+
 void
 set_c_expr_source_range (c_expr *expr,
 location_t start, location_t finish)
@@ -1421,6 +1423,13 @@ c_parser_translation_unit (c_parser *parser)
}
   while (c_parser_next_token_is_not (parser, CPP_EOF));
 }
+
+  for (unsigned i = 0; i < incomplete_record_decls.length (); ++i)
+{
+  tree decl = incomplete_record_decls[i];
+  if (DECL_SIZE (decl) == 0)
+   error ("storage size of %q+D isn%'t known", decl);
+}
 }
 
 /* Parse an external declaration (C90 6.7, C99 6.9).
diff --git a/gcc/c/c-tree.h b/gcc/c/c-tree.h
index 81a3d58..cf79ba7 100644
--- a/gcc/c/c-tree.h
+++ b/gcc/c/c-tree.h
@@ -731,4 +731,6 @@ set_c_expr_source_range (c_expr *expr,
 /* In c-fold.c */
 extern tree decl_constant_value_for_optimization (tree);
 
+extern vec incomplete_record_decls;
+
 #endif /* ! GCC_C_TREE_H */
diff --git a/gcc/testsuite/gcc.dg/Wcxx-compat-8.c 
b/gcc/testsuite/gcc.dg/Wcxx-compat-8.c
index f7e8c55..4e9ddc1 100644
--- a/gcc/testsuite/gcc.dg/Wcxx-compat-8.c
+++ b/gcc/testsuite/gcc.dg/Wcxx-compat-8.c
@@ -33,6 +33,7 @@ enum e3
 
 __typeof__ (struct s5 { int i; }) v5; /* { dg-warning "invalid in C\[+\]\[+\]" 
} */
 __typeof__ (struct t5) w5; /* { dg-bogus "invalid in C\[+\]\[+\]" } */
+  /* { dg-error "storage size of 'w5' isn't known" "" { target *-*-* } 35 } */
 
 int
 f1 (struct s1 *p)
@@ -64,4 +65,4 @@ f5 ()
   return &((struct t8) { });  /* { dg-warning "invalid in C\[+\]\[+\]" } */
 }
 
-/* { dg-error "invalid use of undefined type" "" { target *-*-* } 64 } */
+/* { dg-error "invalid use of undefined type" "" { target *-*-* } 65 } */
diff --git a/gcc/testsuite/gcc.dg/declspec-1.c 
b/gcc/testsuite/gcc.dg/declspec-1.c
index c19f107..9113076 100644
--- a/gcc/testsuite/gcc.dg/declspec-1.c
+++ b/gcc/testsuite/gcc.dg/declspec-1.c
@@ -9,7 +9,8 @@ typedef int t;
 /* These should all be diagnosed, but only once, not for every
identifier declared.  */
 struct s0 int x0, /* { dg-error "two or more data types" } */
-x1;
+/* { dg-error "storage size of 'x0' isn't known" "" { target *-*-* } 11 } */
+x1; /* { dg-error "storage size of 'x1' isn't known" } */ 
 
 char union u0 x2, /* { dg-error "two or more data types" } */
 x3;
diff --git a/gcc/testsuite/gcc.dg/pr24293.c b/gcc/testsuite/gcc.dg/pr24293.c
new file mode 100644
index 000..33285e7
--- /dev/null

Re: reject decl with incomplete struct/union type in check_global_declaration()

[Joseph Myers]

On Fri, 15 Jan 2016, Prathamesh Kulkarni wrote:

> On 15 January 2016 at 03:27, Joseph Myers  wrote:
> > On Thu, 14 Jan 2016, Prathamesh Kulkarni wrote:
> >
> >> Hi,
> >> For test-case containing only the following declaration:
> >> static struct undefined_struct object;
> >> gcc rejects it at -O0 in assemble_variable() with error "storage size
> >> of  is unknown",
> >> however no error is reported when compiled with -O2.
> >
> > Cf bug 24293 (for the -fsyntax-only case) - does this patch fix that?
> Ah this doesn't fix PR24293, it seems analyze_function() doesn't get
> called for -fsyntax-only.
> I don't have a good solution for this. I assume varpool won't be
> populated for -fsyntax-only ?
> And we need to walk over decls with incomplete struct/union types
> after parsing the whole translation unit.
> In the attached patch, I kept a global vec incomplete_record_decls;
> In finish_decl(), if the decl is static, has type struct/union and
> size 0 then it is appened to incomplete_record_decls.
> In c_parser_translation_unit(), iterate over incomplete_record_decls
> and if report error if any decl has size zero.
> The patch passes testsuite.

There's a GNU C extension allowing forward declarations of enums, and it 
seems that

static enum e x;

doesn't get diagnosed either with -fsyntax-only.  Thus I think you should 
cover that case as well.

-- 
Joseph S. Myers
jos...@codesourcery.com

reject decl with incomplete struct/union type in check_global_declaration()

[Prathamesh Kulkarni]

Hi,
For test-case containing only the following declaration:
static struct undefined_struct object;
gcc rejects it at -O0 in assemble_variable() with error "storage size
of  is unknown",
however no error is reported when compiled with -O2.
AFAIU that happens because at -O2, analyze_function() removes the
symbol "object" from symbol table and assemble_variable() has no
chance to process it.
g++ rejects it during parsing. I tried similarly in C FE by adding a
check for decl with incomplete struct/union type in finish_decl(),
however that fails to compile the following case:
typedef struct foo foo_t;
foo_t x;
struct foo { int i; };
g++ rejects the above case as well but gcc accepts it.
Do C and C++ standards differ in this regard ?

So instead of finish_decl(), I added check for incomplete struct/union
in check_global_declaration(),
which is called by analyze_function() before removing unused nodes.
The patch regresses Wcxx-compat-8.c and declspecs-1.c because the error
"storage size of  is unknown" shows up in these test-cases. I
modified the test-cases
to accept that error.
Does the patch look OK ?

Thank you,
Prathamesh
diff --git a/gcc/cgraphunit.c b/gcc/cgraphunit.c
index 950f6c5..1560a78 100644
--- a/gcc/cgraphunit.c
+++ b/gcc/cgraphunit.c
@@ -974,6 +974,12 @@ check_global_declaration (symtab_node *snode)
   ? OPT_Wunused_const_variable
   : OPT_Wunused_variable),
"%qD defined but not used", decl);
+
+  if (VAR_P (decl) && !DECL_EXTERNAL (decl)
+  && RECORD_OR_UNION_TYPE_P (TREE_TYPE (decl)) && DECL_SIZE (decl) == 0)
+{
+  error ("storage size of %q+D isn%'t known", decl);
+}
 }
 
 /* Discover all functions and variables that are trivially needed, analyze
diff --git a/gcc/testsuite/gcc.dg/Wcxx-compat-8.c 
b/gcc/testsuite/gcc.dg/Wcxx-compat-8.c
index f7e8c55..4e9ddc1 100644
--- a/gcc/testsuite/gcc.dg/Wcxx-compat-8.c
+++ b/gcc/testsuite/gcc.dg/Wcxx-compat-8.c
@@ -33,6 +33,7 @@ enum e3
 
 __typeof__ (struct s5 { int i; }) v5; /* { dg-warning "invalid in C\[+\]\[+\]" 
} */
 __typeof__ (struct t5) w5; /* { dg-bogus "invalid in C\[+\]\[+\]" } */
+  /* { dg-error "storage size of 'w5' isn't known" "" { target *-*-* } 35 } */
 
 int
 f1 (struct s1 *p)
@@ -64,4 +65,4 @@ f5 ()
   return &((struct t8) { });  /* { dg-warning "invalid in C\[+\]\[+\]" } */
 }
 
-/* { dg-error "invalid use of undefined type" "" { target *-*-* } 64 } */
+/* { dg-error "invalid use of undefined type" "" { target *-*-* } 65 } */
diff --git a/gcc/testsuite/gcc.dg/declspec-1.c 
b/gcc/testsuite/gcc.dg/declspec-1.c
index c19f107..9113076 100644
--- a/gcc/testsuite/gcc.dg/declspec-1.c
+++ b/gcc/testsuite/gcc.dg/declspec-1.c
@@ -9,7 +9,8 @@ typedef int t;
 /* These should all be diagnosed, but only once, not for every
identifier declared.  */
 struct s0 int x0, /* { dg-error "two or more data types" } */
-x1;
+/* { dg-error "storage size of 'x0' isn't known" "" { target *-*-* } 11 } */
+x1; /* { dg-error "storage size of 'x1' isn't known" } */ 
 
 char union u0 x2, /* { dg-error "two or more data types" } */
 x3;
diff --git a/gcc/testsuite/gcc.dg/struct-incompl-2.c 
b/gcc/testsuite/gcc.dg/struct-incompl-2.c
new file mode 100644
index 000..f3957eb
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/struct-incompl-2.c
@@ -0,0 +1,10 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+static struct foo x;  /* { dg-error "storage size of 'x' isn't known" } */
+static union bar y;  /* { dg-error "storage size of 'y' isn't known" } */
+
+typedef struct P p;
+static p p_obj;  /* { dg-error "storage size of 'p_obj' isn't known" } */
+
+extern struct undefined_object object;


ChangeLog
Description: Binary data

Re: reject decl with incomplete struct/union type in check_global_declaration()

[Joseph Myers]

On Thu, 14 Jan 2016, Prathamesh Kulkarni wrote:

> Hi,
> For test-case containing only the following declaration:
> static struct undefined_struct object;
> gcc rejects it at -O0 in assemble_variable() with error "storage size
> of  is unknown",
> however no error is reported when compiled with -O2.

Cf bug 24293 (for the -fsyntax-only case) - does this patch fix that?

> g++ rejects it during parsing. I tried similarly in C FE by adding a
> check for decl with incomplete struct/union type in finish_decl(),
> however that fails to compile the following case:
> typedef struct foo foo_t;
> foo_t x;
> struct foo { int i; };
> g++ rejects the above case as well but gcc accepts it.
> Do C and C++ standards differ in this regard ?

I don't know about C++, but this sort of thing is valid C if the type is 
complete at the end of the translation unit or is an incomplete array type 
(but not in the case where the variable is static - such a case with 
static, if supported, is an extension).

-- 
Joseph S. Myers
jos...@codesourcery.com

Re: reject decl with incomplete struct/union type in check_global_declaration()

[Nathan Sidwell]

On 01/14/16 16:57, Joseph Myers wrote:

On Thu, 14 Jan 2016, Prathamesh Kulkarni wrote:



g++ rejects it during parsing. I tried similarly in C FE by adding a
check for decl with incomplete struct/union type in finish_decl(),
however that fails to compile the following case:
typedef struct foo foo_t;
foo_t x;
struct foo { int i; };
g++ rejects the above case as well but gcc accepts it.
Do C and C++ standards differ in this regard ?


I don't know about C++, but this sort of thing is valid C if the type is
complete at the end of the translation unit or is an incomplete array type
(but not in the case where the variable is static - such a case with
static, if supported, is an extension).


It's ill-formed C++.

7.1.1/8 allows you to use a declared but undefined struct with 'extern', but not 
 without it.


'The name of a declared but undefined class can be used in an extern 
declaration. Such a declaration can only be used in ways that do not require a 
complete class type'


(Although it doesn't seem to explicitly say that such a name can be used without 
an 'extern', the implication is that it cannot).


nathan