Stop using error_at_line()

.gitignore

@@ -17,3 +17,4 @@ Makefile.in
 Makefile
 .[^.]*
 *.tar.gz
+*~

.travis.yml

@@ -0,0 +1,17 @@
+language: c
+compiler:
+    - gcc
+matrix:
+    include:
+        - os: linux
+          dist: xenial
+        - os: linux
+          dist: trusty
+        - os: linux
+          dist: bionic
+        - os: osx
+script:
+    - autoreconf -i -f
+    - ./configure --enable-debug
+    - make
+    - make check

lib/util/num_test.c

@@ -23,9 +23,10 @@
  */
 
 #include <assert.h>
-#include <error.h>
 #include <stdlib.h>
 #include <string.h>
+#include <errno.h>
+#include <stdio.h>
 #include "hidrd/util/num.h"
 
 #define FMT_u32 "%u"
@@ -36,7 +37,12 @@
 #define FMT_s8  "%hhd"
 
 #define ERROR(_fmt, _args...) \
-    error_at_line(1, 0, __FILE__, __LINE__, _fmt, ##_args)
+    do {                                                        \
+        fprintf(stderr, "%s:%s:%u: " _fmt "\n",                 \
+                program_invocation_name, __FILE__, __LINE__,    \
+                ##_args);                                       \
+        exit(1);                                                \
+    } while (0)
 
 #define PASS_FROM_STR(_t, _v, _s, _m, _b) \
     do {                                                        \

lib/util/ttbl_test.c

@@ -24,14 +24,22 @@
 
 #include <assert.h>
 #include <errno.h>
-#include <error.h>
 #include <stdlib.h>
 #include <string.h>
 #include <stdio.h>
 #include "hidrd/util/ttbl.h"
 
 #define ERROR(_errno, _fmt, _args...) \
-    error_at_line(1, _errno, __FILE__, __LINE__, _fmt, ##_args)
+    do {                                                        \
+        fprintf(stderr, "%s:%s:%u: " _fmt,                      \
+                program_invocation_name, __FILE__, __LINE__,    \
+                ##_args);                                       \
+        if ((_errno) != 0) {                                    \
+            fprintf(stderr, ": %s", strerror(_errno));          \
+        }                                                       \
+        fprintf(stderr, "\n");                                  \
+        exit(1);                                                \
+    } while (0)
 
 #define CHECK_RENDER(_expected) \
     do {                                                                \