[Bug target/49202] New: MMIX: Wrong debugging information generated (UNKNOWN: length 2)

[nils@script-solution.de]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=49202

           Summary: MMIX: Wrong debugging information generated (UNKNOWN:
                    length 2)
           Product: gcc
           Version: 4.6.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: target
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: nils@script-solution.de
              Host: Ubuntu on x86_64
            Target: MMIX
             Build: gcc-4.6.0 with binutils-2.21


Created attachment 24381
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24381
Generated object file

Some C constructs seem to cause wrong debugging information. That is especially
a problem, because gdb ignores all the following information, so that debugging
is impossible (line by line in C source).

For example, the following C source causes the problem:
----
static int strncmpx(const char *str1,const char *str2,int count) {
    int rem = count;
    while(*str1 && *str2 && rem-- > 0) {
        if(*str1++ != *str2++)
            return str1[-1] < str2[-1] ? -1 : 1;
    }
    if(rem <= 0)
        return 0;
    if(*str1 && !*str2)
        return 1;
    return -1;
}

int main(void) {
    strncmpx("foo","bar",3);
    return 0;
}
----

Compiling this file and reading the line number information results in:
$ mmix-elf-escape-gcc -o t.o -c t.c -g
$ mmix-elf-escape-readelf --debug-dump=decodedline t.o
readelf: Warning: unable to apply unsupported reloc type 5 to section
debug_line
Decoded dump of debug contents of section .debug_line:

CU: t.c:
File name                            Line number    Starting address
t.c                                            1                   0

t.c                                            2                0x28
t.c                                            3                0x38
t.c                                            4                0x3c
t.c                                            5                0xa8
UNKNOWN: length 2
t.c                                            5                0xe0
UNKNOWN: length 2
t.c                                            5                0xe8
UNKNOWN: length 2
t.c                                            5                0xec
UNKNOWN: length 2
t.c                                            3                0xf0
UNKNOWN: length 2
t.c                                            3               0x10c
UNKNOWN: length 2
t.c                                            3               0x128
t.c                                            7               0x16c
t.c                                            8               0x184
t.c                                            9               0x18c
UNKNOWN: length 2
t.c                                            9               0x1a8
t.c                                           10               0x1c4
t.c                                           11               0x1cc
t.c                                           12               0x1d0
t.c                                           14               0x1dc
t.c                                           15               0x1ec
t.c                                           16               0x218
t.c                                           17               0x21c


I've attached the object file t.o.