[Bug c/63591] New: No syntax error yielded for semicolons inside a function proto, instead code with memory corruption can be created

[Bug c/63591] New: No syntax error yielded for semicolons inside a function proto, instead code with memory corruption can be created

[k.s.matheussen at notam02 dot no]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63591

            Bug ID: 63591
           Summary: No syntax error yielded for semicolons inside a
                    function proto, instead code with memory corruption
                    can be created
           Product: gcc
           Version: 4.8.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: k.s.matheussen at notam02 dot no

This code should, as far as I know, not be legal C code:

extern int afunction(
                     int anint,
                     struct Happ *happ; // <- Extra semicolon
                     );

int afunction(
              int velocityvelocity,
              struct Happ *happ
              )
{
  return 208;
}


Gcc does not complain about this code, even with -Wall and -Werror.

I'm also seeing memory corruption in a larger program I'm working on,
because of this extra misplaced semicolon, but I haven't been able
to create a smaller example doing this. Please let me know if you need
the larger example causing memory corruption.

I consider this bug (I assume it is a bug) quite serious.
If adding this extra semicolon by mistake (like I did), things appear
to work as normal, whille possibly getting serious bugs which are
hard to trace.

[Bug c/63591] No syntax error yielded for semicolons inside a function proto, instead code with memory corruption can be created

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63591

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |INVALID

--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
https://gcc.gnu.org/onlinedocs/gcc/Variable-Length.html

[Bug c/63591] No syntax error yielded for semicolons inside a function proto, instead code with memory corruption can be created

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63591

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |manu at gcc dot gnu.org

--- Comment #2 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---


(In reply to Kjetil Matheussen from comment #0)
> This code should, as far as I know, not be legal C code:
> 
> extern int afunction(
>                      int anint,
>                      struct Happ *happ; // <- Extra semicolon
>                      );
> 
> int afunction(
>               int velocityvelocity,
>               struct Happ *happ
>               )
> {
>   return 208;
> }
> 
> 
> Gcc does not complain about this code, even with -Wall and -Werror.

GCC 5.0 complains by default.

manuel@gcc10:~$ ~/test1/216257/build/gcc/cc1 test.c  
test.c:9:15: warning: ‘struct Happ’ declared inside parameter list
               )
               ^
test.c:9:15: warning: its scope is only this definition or declaration, which
is probably not what you want

(The location is a bit off, yes).
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From: "k.s.matheussen at notam02 dot no" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/63591] No syntax error yielded for semicolons inside a function proto, instead code with memory corruption can be created
Date: Sat, 18 Oct 2014 23:05:00 -0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idc591

--- Comment #3 from Kjetil Matheussen <k.s.matheussen at notam02 dot no> ---
I didn't know about this gnu extension. But regardless, shouldn't gcc complain
when the proto doesn't match the function itself?

Also, although I don't understand how this extension works from the
documentation, I have a feeling that there should have been a warning or error
when compiling code calling "afunction" as well?

int main(){
  return afunction(5, NULL);
}

(this compiles just fine)

[Bug c/63591] No syntax error yielded for semicolons inside a function proto, instead code with memory corruption can be created

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63591

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|RESOLVED                    |REOPENED
   Last reconfirmed|                            |2014-10-18
         Resolution|INVALID                     |---
     Ever confirmed|0                           |1

--- Comment #4 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
Ah, I get it know. Your testcase was not complete. Please follow
https://gcc.gnu.org/bugs/ when reporting bugs. You will avoid a lot of
confusion.

A complete minimal testcase:

struct Happ;
extern int afunction(
                     int anint,
                     struct Happ *happ; // <- Extra semicolon
                     );

I think we should warn for this case, or even not accept it at all. The above
is clearly not the use intended for VLAs because:

1) happ cannot be the length of the array
2) there are no arguments to the function, so a foward declaration is useless.


If you *really* think this is a serious bug, why not help us to fix it?
https://gcc.gnu.org/wiki/GettingStarted#Basics:_Contributing_to_GCC_in_10_easy_steps
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To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/63591] No syntax error yielded for semicolons inside a function proto, instead code with memory corruption can be created
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idc591

--- Comment #5 from Kjetil Matheussen <k.s.matheussen at notam02 dot no> ---
Sorry, complete example below. The problem with the code is:

1. Proto doesn't match function. There is an extra semicolon in the proto, but
not in the function itself.
2. Calling "afunction" may cause memory corruption, although it is not clear to
me how or why, and I can't reproduce it in a minimal example. I can provide a
larger program that demonstrate this memory corruption though.



struct Happ{
  int a;
  int b[203];
};

extern int afunction(
                     int anint,
                     struct Happ *happ; // <- Problem 1. Extra semicolon.
                     );

int afunction(
              int velocityvelocity,
              struct Happ *hepp
              )
{
  return 208;
}

int main(){
  struct Happ happ;
  return afunction(50,&happ); // <- Problem 2.
}

[Bug c/63591] be more strict when accepting parameter forward declarations

[manu at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63591

Manuel López-Ibáñez <manu at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |diagnostic
            Summary|No syntax error yielded for |be more strict when
                   |semicolons inside a         |accepting parameter forward
                   |function proto, instead     |declarations
                   |code with memory corruption |
                   |can be created              |

--- Comment #6 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Kjetil Matheussen from comment #3)
> I didn't know about this gnu extension. But regardless, shouldn't gcc
> complain when the proto doesn't match the function itself?

Unfortunately, there is [*] too much old code that would break if we did so.
But you can use -Wstrict-prototypes.

[*] or there was, perhaps we should revisit adding -Wstrict-prototypes to
-Wall. But to do that we need someone that will propose such a patch, fix any
failing testcases in the testsuite and convince the maintainers.

> Also, although I don't understand how this extension works from the
> documentation, I have a feeling that there should have been a warning or
> error when compiling code calling "afunction" as well?
> 
> int main(){
>   return afunction(5, NULL);
> }
> 
> (this compiles just fine)

This is because int foo(); is not a prototype (you can call it with foo(5,5)).
You need -Wstrict-prototypes.
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idW925

Paolo Carlini <paolo.carlini at oracle dot com> changed:

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----------------------------------------------------------------------------
             Status|ASSIGNED                    |NEW
           Assignee|paolo.carlini at oracle dot com    |unassigned at gcc dot gnu.org

[Bug c/63591] be more strict when accepting parameter forward declarations

[schwab@linux-m68k.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63591

--- Comment #7 from Andreas Schwab <schwab@linux-m68k.org> ---
A function declaration with forward declared parameters it is a prototype, sort
of.  Not defining the forward declared parameter as a real parameter should
probably be flagged as an error.

[Bug c/63591] be more strict when accepting parameter forward declarations

[manu at gcc dot gnu.org]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="UTF-8", Size: 4610 bytes --]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63591

--- Comment #8 from Manuel López-Ibáñez <manu at gcc dot gnu.org> ---
(In reply to Andreas Schwab from comment #7)
> A function declaration with forward declared parameters it is a prototype,
> sort of.  Not defining the forward declared parameter as a real parameter
> should probably be flagged as an error.

Indeed. Still someone has to implement it... Kjetil?
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Subject: [Bug target/63594] New: [5 Regression] ICE: in ix86_vector_duplicate_value, at config/i386/i386.c:39831 with -mavx512f
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idc594

            Bug ID: 63594
           Summary: [5 Regression] ICE: in ix86_vector_duplicate_value, at
                    config/i386/i386.c:39831 with -mavx512f
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
          Assignee: unassigned at gcc dot gnu.org
          Reporter: zsojka at seznam dot cz

Created attachment 33758
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id3758&actioníit
reduced testcase

Compiler output:
$ gcc -mavx512f testcase.c
testcase.c: In function 'foo_1':
testcase.c:6:11: internal compiler error: in ix86_vector_duplicate_value, at
config/i386/i386.c:39831
   __v64qi v1 = {
           ^
0xe76c32 ix86_vector_duplicate_value
        /mnt/svn/gcc-trunk/gcc/config/i386/i386.c:39831
0xe82543 ix86_expand_vector_init_duplicate
        /mnt/svn/gcc-trunk/gcc/config/i386/i386.c:39956
0xec2823 ix86_expand_vector_init(bool, rtx_def*, rtx_def*)
        /mnt/svn/gcc-trunk/gcc/config/i386/i386.c:40739
0x100628d gen_vec_initv64qi(rtx_def*, rtx_def*)
        /mnt/svn/gcc-trunk/gcc/config/i386/sse.md:17488
0x8bcfe6 insn_gen_fn::operator()(rtx_def*, rtx_def*) const
        /mnt/svn/gcc-trunk/gcc/recog.h:308
0x8bcfe6 store_constructor
        /mnt/svn/gcc-trunk/gcc/expr.c:6456
0x8bebc6 expand_constructor
        /mnt/svn/gcc-trunk/gcc/expr.c:7873
0x8a3b0a expand_expr_real_1(tree_node*, rtx_def*, machine_mode,
expand_modifier, rtx_def**, bool)
        /mnt/svn/gcc-trunk/gcc/expr.c:9711
0x8b2e83 store_expr(tree_node*, rtx_def*, int, bool)
        /mnt/svn/gcc-trunk/gcc/expr.c:5341
0x8ba2da expand_assignment(tree_node*, tree_node*, bool)
        /mnt/svn/gcc-trunk/gcc/expr.c:5127
0x7a14d8 expand_gimple_stmt_1
        /mnt/svn/gcc-trunk/gcc/cfgexpand.c:3278
0x7a14d8 expand_gimple_stmt
        /mnt/svn/gcc-trunk/gcc/cfgexpand.c:3374
0x7a6a56 expand_gimple_basic_block
        /mnt/svn/gcc-trunk/gcc/cfgexpand.c:5209
0x7a8b06 execute
        /mnt/svn/gcc-trunk/gcc/cfgexpand.c:5815
Please submit a full bug report,
with preprocessed source if appropriate.
Please include the complete backtrace with any bug report.
See <http://gcc.gnu.org/bugs.html> for instructions.

Tested revisions:
r216429 - ICE
4_9 r213788 - OK

[Bug c/63591] be more strict when accepting parameter forward declarations

[jsm28 at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63591

Joseph S. Myers <jsm28 at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|REOPENED                    |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #9 from Joseph S. Myers <jsm28 at gcc dot gnu.org> ---
As far as I can tell, the bug discussed here is bug 23144.

*** This bug has been marked as a duplicate of bug 23144 ***