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dnl * If mmap() plays nicely with write()
AC_DEFUN([DOVECOT_MMAP_WRITE], [
AC_CACHE_CHECK([whether shared mmaps get updated by write()s],i_cv_mmap_plays_with_write,[
AC_TRY_RUN([
#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <string.h>
int main() {
/* return 0 if we're signed */
int f = open("conftest.mmap", O_RDWR|O_CREAT|O_TRUNC, 0600);
void *mem;
if (f == -1) {
perror("open()");
return 1;
}
unlink("conftest.mmap");
write(f, "1", 2);
mem = mmap(NULL, 2, PROT_READ|PROT_WRITE, MAP_SHARED, f, 0);
if (mem == MAP_FAILED) {
perror("mmap()");
return 1;
}
strcpy(mem, "2");
msync(mem, 2, MS_SYNC);
lseek(f, 0, SEEK_SET);
write(f, "3", 2);
return strcmp(mem, "3") == 0 ? 0 : 1;
}
], [
i_cv_mmap_plays_with_write=yes
], [
i_cv_mmap_plays_with_write=no
])
])
if test $i_cv_mmap_plays_with_write = no; then
AC_DEFINE(MMAP_CONFLICTS_WRITE,, [Define if shared mmaps don't get updated by write()s])
fi
])
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