Clean-up error message and test

Refactoring error messages:
 - standardize error messages and functions
 - return on error instead of exit
 - test error when target doesn't exist
 - include ability to capture stderr and stdout in the tests

1 files changed, 12 insertions, 0 deletions

diff --git a/common/util.h b/common/util.h
index 102b55b..ad2192b 100644
--- a/common/util.h
+++ b/common/util.h
@@ -8,6 +8,7 @@
 
 #include <string.h>
 #include <stdint.h>
+#include <errno.h>
 
 #define BIT(n)			(1UL << (n))
 
@@ -33,6 +34,17 @@ void debug(const char *format, ...);
 		exit(EXIT_FAILURE);					\
 	} while (0)
 
+#define ret_err(e, ...)                                             \
+	do {                                                        \
+		if (errno == 0) {                                   \
+			err(__VA_ARGS__);                           \
+		} else {                                            \
+			fprintf(stderr, __VA_ARGS__);               \
+			fprintf(stderr, ": %s\n", strerror(errno)); \
+		}                                                   \
+		return (e);                                         \
+	} while (0)
+
 /**
  * From the Linux kernel, include/linux/log2.h:
  *