Be more correct in read_from_stdin()

From read(2) manual page on OpenBSD:

     Error checks should explicitly test for -1.  Code such as

           while ((nr = read(fd, buf, sizeof(buf))) > 0)

     is not maximally portable, as some platforms allow for nbytes to range
     between SSIZE_MAX and SIZE_MAX - 2, in which case the return value of an
     error-free read() may appear as a negative number distinct from -1.
     Proper loops should use

           while ((nr = read(fd, buf, sizeof(buf))) != -1 && nr != 0)

Distingushing between error and eof would also help for debugging.

1 files changed, 4 insertions, 1 deletions

diff --git a/src/util.c b/src/util.c
index 6d10c00..9294f51 100644
--- a/src/util.c
+++ b/src/util.c
@@ -31,7 +31,10 @@ size_t read_from_stdin(void **buffer) {
 
   for(*buffer = NULL; (*buffer = realloc((p = *buffer), len + step));
       len += (size_t)r) {
-    if((r = read(STDIN_FILENO, (uint8_t *)*buffer + len, step)) <= 0) {
+    if((r = read(STDIN_FILENO, (uint8_t *)*buffer + len, step)) == -1) {
+      perror(NULL);
+      break;
+    } else if (r == 0) {
       break;
     }
   }