site_archiver@lists.apple.com Delivered-To: darwin-dev@lists.apple.com On Jan 5, 2008, at 8:29 AM, Norm Green wrote: Something like this? steve$ cat write.c #include <stdio.h> #include <unistd.h> #include <stdint.h> #include <stdlib.h> int main( int argc, const char **argv ) { FILE *w = fopen( "foo", "w" ); ASSERT( w ); int32_t num = 0xAABBCCDD; ASSERT( fwrite(&num, 4, 1, w) == 1 ); ASSERT( fflush(w) == 0 ); FILE *r = fopen( "foo", "r" ); ASSERT( r ); ASSERT( fread(&num, 4, 1, r) == 1 ); ASSERT( num == 0xAABBCCDD ); ASSERT( fseek(w, 0, SEEK_SET) == 0 ); num = 0x11223344; ASSERT( fwrite(&num, 1, 1, w) == 1 ); ASSERT( fflush(w) == 0 ); if( argc > 1 ) ASSERT( fpurge(r) == 0 ); ASSERT( fseek(r, 0, SEEK_SET) == 0 ); ASSERT( fread(&num, 1, 1, r) == 1 ); printf( "%#x\n", num ); ASSERT( num == 0x11223344 ); ASSERT( fclose(r) == 0 ); ASSERT( fclose(w) == 0 ); return 0; } steve$ gcc -Wall write.c steve$ ./a.out 0xaa223344 31: num == 0x11223344: Undefined error: 0 steve$ ./a.out foo 0x11223344 -- Steve Checkoway "Anyone who says that the solution is to educate the users hasn't ever met an actual user." -- Bruce Schneier _______________________________________________ Do not post admin requests to the list. They will be ignored. Darwin-dev mailing list (Darwin-dev@lists.apple.com) Help/Unsubscribe/Update your Subscription: http://lists.apple.com/mailman/options/darwin-dev/site_archiver%40lists.appl... This email sent to site_archiver@lists.apple.com I've found what I consider to be a stream IO bug. Here's what's happening: [snip] Is this is a bug? Are there any work arounds? I wouldn't think this is a bug. Stream IO is buffered. Just because you flushed the output doesn't mean you flushed the input. I would expect it to read from its buffer. Try fpurge(3). It seems to be a BSD function, though. I wrote a simple test case to demonstrate this problem, which passes on Solaris. #define STR(x) XSTR(x) #define XSTR(x) #x #define ASSERT( x ) \ do { if( !(x) ) { perror( STR(__LINE__) ": " #x ); exit( 1 ); } } while( 0 ) fpurge(3) seems to advance the file pointer so you have to seek after you purge. smime.p7s