paleofetch

commit 9ae2287dc72c57a768e7a28507cda3c3a954387f
parent f6ae146cd891240813f4d609dfddc1f0d84f81f1
Author: Allis IO <0xa111510@gmail.com>
Date:   Thu, 23 Apr 2020 22:46:11 -0400

Handle cache misses gracefully

If the user changes their config to cache a new value, recompiles, and
then runs paleofetch without `--recache`, we segfault when we go looking
for the new key in the now-stale cache.

This patch fixes that by checking whether `strstr()` found something
and bails if it didn't, guiding the user in the direction of the fix.

Because this seemed like a good use case for a formatted exit message,
`halt_and_catch_fire()` was refactored to behave like `fprintf(stderr, ...)`.

Token-pasting `__VA_ARGS__` is a widely adopted extension (at least, GCC
and Clang have supported it for ages) that I made us of so that I didn't
have to touch any of the other calls to `halt_and_catch_fire()`.
Without the `##`, they'd leave a trailing comma in the expansion and
result in invalid syntax.

Diffstat:
M
paleofetch.c
 | 
18
+++++++++++-------

1 file changed, 11 insertions(+), 7 deletions(-)
diff --git a/paleofetch.c b/paleofetch.c
@@ -4,6 +4,7 @@
 #include <stdbool.h>
 #include <string.h>
 #include <dirent.h>
+#include <errno.h>
 
 #include <sys/utsname.h>
 #include <sys/sysinfo.h>
@@ -29,12 +30,11 @@ struct sysinfo my_sysinfo;
 int title_length;
 int status;
 
-void halt_and_catch_fire(const char *message) {
-    if(status != 0) {
-        printf("paleofetch: %s\n", message);
-        exit(status);
+#define halt_and_catch_fire(fmt, ...) \
+    if(status != 0) { \
+        fprintf(stderr, "paleofetch: " fmt "\n", ##__VA_ARGS__); \
+        exit(status); \
     }
-}
 
 /*
  * Replaces the first newline character with null terminator
@@ -505,9 +505,13 @@ char *get_cache_file() {
  * we might get in trouble would be if the user decided not to have any
  * sort of sigil (like ':') after their labels. */
 char *search_cache(char *cache_data, char *label) {
-    char *start = strstr(cache_data, label) + strlen(label);
+    char *start = strstr(cache_data, label);
+    if(start == NULL) {
+        status = ENODATA;
+        halt_and_catch_fire("cache miss on key '%s'; need to --recache?", label);
+    }
+    start += strlen(label);
     char *end = strchr(start, ';');
-
     char *buf = calloc(1, BUF_SIZE);
     // skip past the '=' and stop just before the ';'
     strncpy(buf, start + 1, end - start - 1);