[LLVMbugs] [Bug 17358] New: raw_ostream.write fails to account for when buffer size is larger than INT_MAX

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=17358

            Bug ID: 17358
           Summary: raw_ostream.write fails to account for when buffer
                    size is larger than INT_MAX
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: FreeBSD
            Status: NEW
          Severity: normal
          Priority: P
         Component: Support Libraries
          Assignee: unassignedbugs at nondot.org
          Reporter: khilan.gudka at cl.cam.ac.uk
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

Dear all

FreeBSD has a restriction that the write() system call can only write up to
INT_MAX (~2GB) bytes and will otherwise return errno 22 (EINVAL).

Adding this code to the start of write(const char *Ptr, size_t Size) in
lib/Support/raw_ostream.cpp seems to do the trick:

#ifdef __FreeBSD__  
  if (LLVM_UNLIKELY(Size > INT_MAX)) {
    write(Ptr, INT_MAX);
    return write(Ptr + INT_MAX, Size - INT_MAX);
  }
#endif

I'm not sure what would be a suitable test case for this except that the
following code will tell you if your particular platform can/cannot write more
than INT_MAX:

#include <fcntl.h>
#include <errno.h>
#include <limits.h>

#define BUF_SIZE 2147483648

char arr[BUF_SIZE];

int main(int argc, char** argv) {
  unsigned int i;
  for (i=0; i<BUF_SIZE; i++) {
    arr[i] = 3;
  }
  int fd = open("dump.txt", O_CREAT | O_RDWR);
  int ret = write(fd, arr, BUF_SIZE);
  if (ret < 0) {
    printf("Error writing: %d\n", errno);
  }
  close(fd);
  return 0;
}

Regards
Khilan

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