On 10/16/13, Edscott Wilson <[email protected]> wrote:
> I've been banging my head against the monitor for the past nine hours and
> narrowed a problem down to the following.
> I've found that for certain data, the read() function will return a short
> byte count.
>
> Take the following test file: http://xffm.org/test.dbh and compile and
> execute the following program:
>
>
> #include <stdio.h>
> #include <stdlib.h>
> #include <sys/types.h>
> #include <sys/stat.h>
> #include <fcntl.h>
> #include <errno.h>
>
>
> int main(int argc, char **argv){
> int fd = open("test.dbh",O_RDWR);
Try adding O_BINARY to the open() flags here.
> void *data = malloc(256);
> size_t bytes = read(fd, data, 256);
> printf("bytes read=%ld\n", (long)bytes);
> printf("errno=%s\n", strerror(errno));
> close(fd);
> FILE *f = fopen("test.dbh", "r");
> bytes = fread(data, 1, 256, f);
> printf("bytes fread=%ld\n", (long)bytes);
> return 1;
> }
>
>
> This is the output of the above program compiled with mingw gcc:
>
> bytes read=255
> errno=No error
> bytes fread=256
>
> Which is wrong. I get the same broken result with both:
> gcc.exe (rev5, Built by MinGW-W64 project) 4.8.1
> and
> gcc.exe (GCC) 4.6.2 (from mingw-32)
>
> Linux, of course, reads the 256 bytes correctly.
>
> So there is something in the file which breaks the read on Windows.
> What could possibly be wrong?
> Is there some Windows trick you need apply to make read() work as it is
> intended?
> Or would it be a bug of the mingw gcc port?
>
> Any help is appreciated.
>
--
O.S.
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