[Bug c/52554] New: Variable called $1 causes invalid asm to be generated

[Bug c/52554] New: Variable called $1 causes invalid asm to be generated

[rwxr-xr-x at gmx dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52554

             Bug #: 52554
           Summary: Variable called $1 causes invalid asm to be generated
    Classification: Unclassified
           Product: gcc
           Version: 4.6.3
            Status: UNCONFIRMED
          Severity: minor
          Priority: P3
         Component: c
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: rwxr-xr-x@gmx.de


The following code is somewhat silly, but gcc should either compile it
correctly or print an error message, not generate invalid asm.

Here's my code:

int $1 = -1;

int main(void) {
    $1++;
    return $1;
}

Here's my command:

% gcc try.c
/tmp/ccVyjhob.s: Assembler messages:
/tmp/ccVyjhob.s:22: Error: operand type mismatch for `mov'

Here's my asm:

    .file    "try.c"
    .globl    $1
    .data
    .align 4
    .type    $1, @object
    .size    $1, 4
$1:
    .long    -1
    .text
    .globl    main
    .type    main, @function
main:
.LFB0:
    .cfi_startproc
    pushl    %ebp
    .cfi_def_cfa_offset 8
    .cfi_offset 5, -8
    movl    %esp, %ebp
    .cfi_def_cfa_register 5
    movl    $1, %eax
    incl    %eax
    movl    %eax, $1
    movl    $1, %eax
    popl    %ebp
    .cfi_def_cfa 4, 4
    .cfi_restore 5
    ret
    .cfi_endproc
.LFE0:
    .size    main, .-main
    .ident    "GCC: (GNU) 4.6.3"
    .section    .note.GNU-stack,"",@progbits

Here's my specs:

% gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/home/mauke/usr/local/libexec/gcc/i686-pc-linux-gnu/4.6.3/lto-wrapper
Target: i686-pc-linux-gnu
Configured with: ../gcc-4.6.3/configure --prefix=/home/mauke/usr/local
--with-arch=native --with-tune=native --enable-__cxa_atexit --disable-nls
--enable-languages=c,c++,go
Thread model: posix
gcc version 4.6.3 (GCC)

[Bug c/52554] Variable called $1 causes invalid asm to be generated

[rguenth at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52554

Richard Guenther <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |accepts-invalid
                 CC|                            |jsm28 at gcc dot gnu.org
          Component|target                      |c

--- Comment #1 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-03-12 13:28:05 UTC ---
C does not allow an identifier to start with a dollar.  But we even accept
the program with -std=c99 -pedantic-errors.

[Bug c/52554] Variable called $1 causes invalid asm to be generated

[schwab@linux-m68k.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52554

--- Comment #2 from Andreas Schwab <schwab@linux-m68k.org> 2012-03-12 14:22:00 UTC ---
6.4.2.1 says that an identifier may contain "other implementation-defined
characters".

[Bug c/52554] Variable called $1 causes invalid asm to be generated

[rwxr-xr-x at gmx dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52554

Lukas Mai <rwxr-xr-x at gmx dot de> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |wrong-code

--- Comment #3 from Lukas Mai <rwxr-xr-x at gmx dot de> 2012-03-13 16:57:38 UTC ---
It gets better:

int $42 = 0;

int main(void) {
    return $42;
}

% gcc try.c; ./a.out; echo $?      
42

% gcc -O2 try.c; ./a.out; echo $?   
42

% gcc -flto try.c; ./a.out; echo $?
/tmp/cc5Gwdzb.s: Assembler messages:
/tmp/cc5Gwdzb.s:13: Error: junk `.1988' after expression
lto-wrapper: gcc returned 1 exit status
/usr/bin/ld: lto-wrapper failed
collect2: ld returned 1 exit status
zsh: no such file or directory: ./a.out
127

% gcc -O -flto try.c; ./a.out; echo $?
0

So compiling this program either
1) generates bogus code,
2) causes assembler syntax errors, or
3) compiles correctly,
depending on which compiler flags are used.

[Bug target/52554] Variable called $1 causes invalid asm to be generated

[fw at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52554

Florian Weimer <fw at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|accepts-invalid, wrong-code |
             Status|UNCONFIRMED                 |RESOLVED
                 CC|                            |fw at gcc dot gnu.org
         Resolution|                            |INVALID

--- Comment #4 from Florian Weimer <fw at gcc dot gnu.org> 2012-03-28 05:38:56 UTC ---
Some platforms (such as VMS) support $ in identifiers, similar to _.  It seems
that your assembler doesn't:

http://gcc.gnu.org/onlinedocs/gcc/Dollar-Signs.html

(If you compile with -pedantic, you'll get a warning.)

This is not much different from platforms where global symbols are
case-insensitive or severely limited in length.

[Bug target/52554] Variable called $1 causes invalid asm to be generated

[webmaster at openhardware dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52554

webmaster at openhardware dot de changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |webmaster at openhardware
                   |                            |dot de

--- Comment #5 from webmaster at openhardware dot de 2012-03-28 09:36:47 UTC ---
Hi, I tested the 42 it mit older gcc, and it behaved better:

 gcc --version
gcc (GCC) 4.2.4 (Gentoo 4.2.4 p1.0)
Copyright (C) 2007 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.


 cat >try.c
int $42 = 0;

int main(void) {
    return $42;
}


 gcc try.c; ./a.out; echo $?  
/tmp/ccY61UFa.s: Assembler messages:
/tmp/ccY61UFa.s:18: Error: junk `(%rip)' after expression
bash: ./a.out: No such file or directory
127

 gcc -O2 try.c; ./a.out; echo $? 
/tmp/ccXk0zWe.s: Assembler messages:
/tmp/ccXk0zWe.s:8: Error: junk `(%rip)' after expression
bash: ./a.out: No such file or directory
127


But I would expect an syntax error thrown by gcc here.

[Bug target/52554] Variable called $1 causes invalid asm to be generated

[rwxr-xr-x at gmx dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52554

--- Comment #6 from Lukas Mai <rwxr-xr-x at gmx dot de> 2012-03-29 11:26:12 UTC ---
>From the gcc documentation:

| However, dollar signs in identifiers are not supported on a few target
| machines, typically because the target assembler does not allow them.

That's nice, but:

|   * If the compiler produces invalid assembly code, for any input
|     whatever (except an `asm' statement), that is a compiler bug,
|     unless the compiler reports errors (not just warnings) which would
|     ordinarily prevent the assembler from being run.

|   * If the compiler produces valid assembly code that does not
|     correctly execute the input source code, that is a compiler bug.

If my target assembler (gas) doesn't allow them, you must produce an error.
Making up asm syntax and handing it to the assembler is not an option.

Alternatively, change the documentation to the effect that invalid assembly
code and valid (but semantically wrong) assembly code aren't necessarily
compiler bugs.

[Bug target/52554] Variable called $1 causes invalid asm to be generated

[webmaster at openhardware dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52554

--- Comment #7 from openhardware <webmaster at openhardware dot de> 2012-03-29 13:40:14 UTC ---
"Alternatively, change the documentation to the effect that invalid assembly
code and valid (but semantically wrong) assembly code aren't necessarily
compiler bugs."

Its a "windows-approach"
Not a bug but a feature.

Intel calls their errata sheets for silicon bugs "specification update"
That's really sweet, so whats a spec for?

Please fix it in gcc to be a syntax error, or at least throw a warning like
"Illegal variable name found in line # might cause illegal assembly code and
thus unpredictable results!".

This would be the best, so if one has a special "geeks-assembler", 
that allows a $ to be send to the assembler, so one could use it, for what
special geeks-reason ever (may be, to have a hack to illegally allign a
variable in memory  between the rails of the processors word length in order to
smear it into two registers [highbyte of lower register and lowbyte of upper
register] of some IO or to do some other dirty stuff directly from hell)

[Bug target/52554] Variable called $1 causes invalid asm to be generated

[rwxr-xr-x at gmx dot de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52554

Lukas Mai <rwxr-xr-x at gmx dot de> changed:

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

--- Comment #8 from Lukas Mai <rwxr-xr-x at gmx dot de> 2012-04-04 03:37:48 UTC ---
According to the documentation this is a valid bug. See
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52554#c6.

[Bug target/52554] Variable called $1 causes invalid asm to be generated

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=52554

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

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

--- Comment #9 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Dup of bug 31782.

*** This bug has been marked as a duplicate of bug 31782 ***