https://sourceware.org/bugzilla/show_bug.cgi?id=29292
--- Comment #2 from Rainer Orth <ro at CeBiTec dot Uni-Bielefeld.DE> ---
> --- Comment #1 from Rainer Orth <ro at gcc dot gnu.org> ---
> I'll try to create a minimal testcase (just tmpfile, mmap, fill buffer, msync,
> munmap, fread) to see if the problem reproduces there.
Here's what I've got:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/mman.h>
#include <unistd.h>
#define headersz 72
int
main (void)
{
FILE *f = tmpfile ();
int fd = fileno (f);
lseek (fd, headersz - 1, SEEK_SET);
char dummy = 0;
write (fd, &dummy, 1);
void *hdr = mmap (NULL, headersz, PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
memset (hdr, 'a', headersz - 1);
msync (hdr, headersz, MS_ASYNC);
munmap (hdr, headersz);
fseek (f, 0, SEEK_END);
long fsize = ftell (f);
fseek (f, 0, SEEK_SET);
unsigned char *buf = malloc (fsize);
fread (buf, fsize, 1, f);
printf ("%s\n", buf);
return 0;
}
It works (printing 71 x 'a') on all of Linux/x86_64, Mac OS X 10.7,
Solaris 10 and Solaris 11.3. Only on Solaris 11.4 do I get an empty
buffer, matching what I see with gld.
> However, I very much wonder what's the advantage of this complicated
> mmap/msync/munmap
> dance instead of just writing the header to the tmp file and be done with it.
Despite the fact that obviously Solaris 11.4 is wrong here, this
question remains valid.
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