[Bug c++/25468] New: -g makes g++ loop forever

[Bug c++/25468] New: -g makes g++ loop forever

[sylvain dot pion at sophia dot inria dot fr]

The attached program compiles fine with "g++" (4.0.3 as of 20051217).
When adding "-g", it looks like it loops forever (at least 15 minutes).

Note that the program does not compile with g++ 4.1 (probably "invalid").


-- 
           Summary: -g makes g++ loop forever
           Product: gcc
           Version: 4.0.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: sylvain dot pion at sophia dot inria dot fr
  GCC host triplet: i686-pc-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug c++/25468] -g makes g++ loop forever

[sylvain dot pion at sophia dot inria dot fr]

------- Comment #1 from sylvain dot pion at sophia dot inria dot fr  2005-12-17 22:26 -------
Created an attachment (id=10522)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=10522&action=view)
preprocessed C++ bzip2 file


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [3.4 Regression] -g makes g++ loop forever

[sylvain dot pion at sophia dot inria dot fr]

------- Comment #2 from sylvain dot pion at sophia dot inria dot fr  2005-12-17 23:26 -------
Created an attachment (id=10523)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=10523&action=view)
Updated test-case

I fixed the test-case so that it compiles (without "-g") with g++ 4.1.
g++ 4.1 shows the same problem (i.e. takes too long with "-g").


-- 

sylvain dot pion at sophia dot inria dot fr changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
  Attachment #10522|0                           |1
        is obsolete|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [3.4 Regression] -g makes g++ loop forever

[pinskia at gcc dot gnu dot org]

------- Comment #3 from pinskia at gcc dot gnu dot org  2005-12-17 23:27 -------
(In reply to comment #2)
> Created an attachment (id=10523)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=10523&action=view) [edit]
> Updated test-case


>From looking at what is happening is that debug info is taking a long time to
output.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [3.4 Regression] -g makes g++ loop forever

[wilson at gcc dot gnu dot org]

------- Comment #4 from wilson at gcc dot gnu dot org  2006-02-08 04:02 -------
The problem here is ASM_OUTPUT_ASCII.

The testcase is a big file with a lot of functions that have long function
names.  It is 4MB of C++ code, producing a 28MB .s file in about 15 seconds. 
If I add -Q and pipe the output to a file, I get 123MB, which means we have a
lot of strings just for the function names.  Adding -g, it takes about 20
minutes to compile the file, producing a .s file of about 108MB.  Of the extra
80MB much of it is going through ASM_OUTPUT_ASCII.

If you look at ASM_OUTPUT_ASCII, you see that the code uses putc to print one
character at a time while checking for characters that need to be quoted.  It
also throws in a lot of extra fprintf calls just to make this even slower.  So
we are trying to feed maybe 70MB through putc, and obviously, that is going to
take a lot of time.

If I hack in a definition of ASM_OUTPUT_ASCII that just uses 3 fputs calls,
then  it compiles in about 16 seconds.  This isn't quite right, as we are
missing quoting for special characters, but this clearly shows that the problem
is here in ASM_OUTPUT_ASCII.

There are some complicating factors here.  Some assemblers can't handle long
lines in the .ascii directive, so we deliberately break up the output into
lines less than 80 characters.  This can perhaps be dropped if we know we are
using GNU as.  We could maybe document the allowed line lengths for other
assemblers instead of assuming it is 80 characters.

ASM_OUTPUT_ASCII is defined in a lot of different files in subtly different
ways, and they all have this problem.

If we can assume that function names never contain special characters that need
quoting, then we can perhaps solve the problem by not using ASM_OUTPUT_ASCII
for this.  We could have a simpler and faster routine that doesn't worry about
the need to emit quoting characters.  This should be true for C.  I'm not sure
about C++ and the other languages.  This is probably a risky assumption to
make.

ASM_OUTPUT_ASCII could be faster if it scanned forward for the next special
character that needs quoting, then then emits everything up to the next special
character via puts (or whatever), modulo the allowed line length.


-- 

wilson at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |wilson at gcc dot gnu dot
                   |                            |org
             Status|UNCONFIRMED                 |NEW
     Ever Confirmed|0                           |1
   Last reconfirmed|0000-00-00 00:00:00         |2006-02-08 04:02:15
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [4.0/4.1/4.2 Regression] -g makes g++ loop forever

[jsm28 at gcc dot gnu dot org]

-- 

jsm28 at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[3.4 Regression] -g makes   |[4.0/4.1/4.2 Regression] -g
                   |g++ loop forever            |makes g++ loop forever
   Target Milestone|---                         |4.1.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [4.0/4.1/4.2 Regression] -g makes g++ loop forever

[mmitchel at gcc dot gnu dot org]

-- 

mmitchel at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [4.0/4.1/4.2 Regression] -g makes g++ loop forever

[steven at gcc dot gnu dot org]

------- Comment #5 from steven at gcc dot gnu dot org  2006-07-22 16:36 -------
We do the loop-and-putc thing in ASM_OUTPUT_LIMITED_STRING and in
dw2_asm_output_nstring as well.  Probably it's best to add some kind of generic
"escaped string" print function, something like the one below that I'll try to
actually make work:

void
asm_output_string_with_escapes (const char *str, size_t len,
                                const char escapes[255],
                                const char *escapes_fmt /* e.g. "\\%03o" */
                                size_t escapes_fmt_len)
{
  size_t i, j, len, escaped_len;
  char *escaped_str;

  escaped_len = len;
  for (i = 0; i < len; i++)
    {
      int c = str[i];
      if (c == '\"' || c == '\\')
        escaped_len++;
      else if (escapes[c])
        escaped_len += escapes_fmt_len;
    }

  str = xmalloc (escaped_len + 1);

  for (i = 0, j = 0; i < len; i++)
    {
      int c = str[i];
      if (!escapes[c])
        {
          if (c == '\"' || c == '\\')
            escaped_str[j++] = '\\';
          escaped_str[j++] = c;
        }
      else
        {
          /* ??? Must also handle things like \t and \b here.  */
          snprintf (&escaped_str[j], escapes_fmt_len, escapes_fmt, c);
          j += escapes_fmt_len;
        }
    }
  escaped_str[j] = '\0';
  fputs (escaped_str, asm_out_file);

  free (escaped_str);
}


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|unassigned at gcc dot gnu   |steven at gcc dot gnu dot
                   |dot org                     |org
             Status|NEW                         |ASSIGNED
   Last reconfirmed|2006-02-08 04:02:15         |2006-07-22 16:36:32
               date|                            |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [4.0/4.1/4.2 Regression] -g makes g++ loop forever

[steven at gcc dot gnu dot org]

------- Comment #6 from steven at gcc dot gnu dot org  2006-07-23 11:51 -------
Consider these lines in elfos.h:ASM_OUTPUT_ASCII:

                                                                        \
          for (p = _ascii_bytes; p < limit && *p != '\0'; p++)          \
            continue;                                                   \
                                                                        \

Now take a string of 40000+ characters with no '\0' terminator.  This will
trigger quadratic behavior. We'll go look for a 0 terminator thousands of time
and not find it.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [4.0/4.1/4.2 Regression] -g makes g++ loop forever

[steven at gcc dot gnu dot org]

------- Comment #7 from steven at gcc dot gnu dot org  2006-07-23 13:11 -------
Happens on at least all the targets that includes elfos.h, cris/aout.h,
i386/ptx4-i.h, i386/i386-interix.h, i386/sysv4.h, i386/i386elf.h.

I'm only fixing elfos.h, but others can copy over the same idea.


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   GCC host triplet|i686-pc-linux-gnu           |


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [4.0/4.1/4.2 Regression] -g makes g++ loop forever

[steven at gcc dot gnu dot org]

------- Comment #8 from steven at gcc dot gnu dot org  2006-07-23 14:54 -------
Created an attachment (id=11925)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=11925&action=view)
proposed fix, nukes quadratic behavior 

needs detailed testing, but this cuts the time spent in debug info writing to
almost nothing.  Or, for targets that use the defitition of ASM_OUTPUT_ASCII
that is in config/elfos.h, anyway.


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [4.0/4.1/4.2 Regression] -g makes g++ loop forever

[steven at gcc dot gnu dot org]

------- Comment #9 from steven at gcc dot gnu dot org  2006-07-23 17:56 -------
Subject: Bug 25468

Author: steven
Date: Sun Jul 23 17:56:34 2006
New Revision: 115685

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=115685
Log:
2006-07-23  Steven Bosscher  <steven@gcc.gnu.org>

        PR debug/25468
        * config/elfos.h (ASM_OUTPUT_ASCII): Remove 'register' marks.
        Cache the last found '\0' marker to avoid quadratic behavior.

Modified:
    trunk/gcc/ChangeLog
    trunk/gcc/config/elfos.h
    trunk/gcc/fortran/ChangeLog
    trunk/gcc/testsuite/gfortran.fortran-torture/execute/der_init_4.f90


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [4.0/4.1 Regression] -g makes g++ loop forever

[steven at gcc dot gnu dot org]

------- Comment #10 from steven at gcc dot gnu dot org  2006-07-23 17:57 -------
Fixed on the trunk.


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[4.0/4.1/4.2 Regression] -g |[4.0/4.1 Regression] -g
                   |makes g++ loop forever      |makes g++ loop forever


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [4.0/4.1 Regression] -g makes g++ loop forever

[steven at gcc dot gnu dot org]

------- Comment #11 from steven at gcc dot gnu dot org  2006-07-31 22:08 -------
Subject: Bug 25468

Author: steven
Date: Mon Jul 31 22:08:47 2006
New Revision: 115841

URL: http://gcc.gnu.org/viewcvs?root=gcc&view=rev&rev=115841
Log:
        PR debug/25468
        Backport from mainline
        * config/elfos.h (ASM_OUTPUT_ASCII): Remove 'register' marks.
        Cache the last found '\0' marker to avoid quadratic behavior.

Modified:
    branches/gcc-4_1-branch/gcc/ChangeLog
    branches/gcc-4_1-branch/gcc/config/elfos.h


-- 


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [4.0 Regression] -g makes g++ loop forever

[pinskia at gcc dot gnu dot org]

-- 

pinskia at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.1.2                       |4.0.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [4.0 Regression] -g makes g++ loop forever

[steven at gcc dot gnu dot org]

-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|4.1.2                       |4.0.4


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [4.0 Regression] -g makes g++ loop forever

[steven at gcc dot gnu dot org]

------- Comment #12 from steven at gcc dot gnu dot org  2006-07-31 22:13 -------
Fixed in GCC 4.2 and GCC 4.1.  But I am not interested in fixing this in GCC
4.0, so I'm finished with this bug.


-- 

steven at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         AssignedTo|steven at gcc dot gnu dot   |unassigned at gcc dot gnu
                   |org                         |dot org
             Status|ASSIGNED                    |NEW
   Target Milestone|4.0.4                       |4.1.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468

[Bug debug/25468] [4.0 Regression] -g makes g++ loop forever

[gdr at gcc dot gnu dot org]

------- Comment #13 from gdr at gcc dot gnu dot org  2007-02-03 16:09 -------
Fixed in GCC-4.1.2 and higher.


-- 

gdr at gcc dot gnu dot org changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |RESOLVED
         Resolution|                            |FIXED
   Target Milestone|4.0.4                       |4.1.2


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25468