wrap fgets to retry on EINTR

The read() underlying fgets() can be interrupted by a signal handler
causing fgets() to return NULL.  Before we started handling SIGWINCH,
the odds of interrupting a read were low and typically resulted in
termination anyway.  Replace all fgets calls with a wrapper that retries
in EINTR.

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>

2 files changed, 28 insertions, 0 deletions

diff --git a/src/common/util-common.c b/src/common/util-common.c
index 3316eaec..ab74e7c6 100644
--- a/src/common/util-common.c
+++ b/src/common/util-common.c
@@ -17,6 +17,7 @@
  *  along with this program.  If not, see <http://www.gnu.org/licenses/>.
  */
 
+#include <errno.h>
 #include <stdlib.h>
 #include <string.h>
 
@@ -102,6 +103,30 @@ int llstat(char *path, struct stat *buf)
 	return ret;
 }
 
+/** Wrapper around fgets() which properly handles EINTR
+ * @param s string to read into
+ * @param size maximum length to read
+ * @param stream stream to read from
+ * @return value returned by fgets()
+ */
+char *safe_fgets(char *s, int size, FILE *stream)
+{
+	char *ret;
+	int errno_save = errno, ferror_save = ferror(stream);
+	while((ret = fgets(s, size, stream)) == NULL && !feof(stream)) {
+		if(errno == EINTR) {
+			/* clear any errors we set and try again */
+			errno = errno_save;
+			if(!ferror_save) {
+				clearerr(stream);
+			}
+		} else {
+			break;
+		}
+	}
+	return ret;
+}
+
 #ifndef HAVE_STRNDUP
 /* A quick and dirty implementation derived from glibc */
 /** Determines the length of a fixed-size string.
diff --git a/src/common/util-common.h b/src/common/util-common.h
index 576702fa..ca8db5ab 100644
--- a/src/common/util-common.h
+++ b/src/common/util-common.h
@@ -20,6 +20,7 @@
 #ifndef _PM_UTIL_COMMON_H
 #define _PM_UTIL_COMMON_H
 
+#include <stdio.h>
 #include <sys/stat.h> /* struct stat */
 
 const char *mbasename(const char *path);
@@ -27,6 +28,8 @@ char *mdirname(const char *path);
 
 int llstat(char *path, struct stat *buf);
 
+char *safe_fgets(char *s, int size, FILE *stream);
+
 #ifndef HAVE_STRNDUP
 char *strndup(const char *s, size_t n);
 #endif