On Fri, May 05, 2006 at 11:08:31PM +0200, Michael Kerrisk wrote:
> > > Hmmm -- I'm not seeing this. Can you post for each of the two
> > > test cases:
> > >
> > > -- the fopen() call that is used.
> > >
> > > -- the command line that is used to run the program.
> > >
> > > -- the results of grep the strace output using:
> > >
> > > egrep '(mmap|open|read)'
> > Sure, (using strace -e mmap2,open,read instead):
> >
> > fopen "r":
> > |...
> > |open("/tmp/fp.c", O_RDONLY) = 3
> > |mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
> > = 0xb7f3a000
> > |read(3, "#include <sys/types.h>\n#include "..., 4096) = 460
> > |read(3, "", 4096) = 0
> >
> > fopen "r+m":
> > |...
> > |open("/tmp/fp.c", O_RDWR) = 3
> > |mmap2(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0)
> > = 0xb7f8e000
> > |read(3, "#include <sys/types.h>\n#include "..., 4096) = 462
> > |read(3, "", 4096) = 0
> >
> > fopen "rm":
> > |...
> > |open("/tmp/fp.c", O_RDONLY) = 3
> > |mmap2(NULL, 461, PROT_READ, MAP_SHARED, 3, 0) = 0xb7f1c000
>
> Okay -- that look good. But it's strange, I'm not seeing the
> same as you on SUSE 10.0, glibc 2.3.5. Do you have another Linux
> to hand to test?
I just tested on another Debian machine with the same results for
fopen "rm".
But another machine did only an anonymous mmap:
2.6.12-1-amd64-k8-smp
glibc 2.3.6
I note the following differences:
Native POSIX Threads Library by Ulrich Drepper et al and
libthread_db work sponsored by Alpha Processor Inc
vs.
linuxthreads-0.10 by Xavier Leroy (on kobun64).
On a 32 bit radhat machine, the same thing; this time, linuxthreads
and libthread_db. Linux 2.4.22-1.2199.nptl and glibc 2.3.3.
Alan didn't have strace installed on a different redhat machine, so I
copied mine, and again it didn't mmap the file. Again, linuxthreads
and libthread_db. glibc 2.3.3, and Linux 2.6.10-1.771_FC2.
I note that this functionality requires the compile-time conditional
_G_HAVE_MMAP.
Justin
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