testsuite: reshuffle preload env. variable handling

Get the existing LD_PRELOAD early and do a two pass on the rest.

Effectively calculate the total length, allocate and copy... Instead of
the existing recalc, realloc, copy.

Fewer allocations (failure points), while also being a bit simpler and
shorter code.

v2:
 - append existing ldpreload

v3:
 - revert to prepending, do so only as needed

Signed-off-by: Emil Velikov <emil.l.velikov@gmail.com>
Link: https://github.com/kmod-project/kmod/pull/429
Signed-off-by: Lucas De Marchi <demarchi@kernel.org>

diff --git a/testsuite/testsuite.c b/testsuite/testsuite.c
index 7dd6fe228a96c09a33e049d3b25e06ba8632ab2e..9f96ef944002dcf6d057a48b5a592b07df19dce5 100644 (file)
--- a/testsuite/testsuite.c
+++ b/testsuite/testsuite.c
@@ -168,55 +168,52 @@ int test_spawn_prog(const char *prog, const char *const args[])
 
 static void test_export_environ(const struct test *t)
 {
-       _cleanup_free_ char *preload = NULL;
-       size_t preloadlen = 0;
-       size_t i;
+       const char *existing_preload = getenv("LD_PRELOAD");
+       size_t existing_preload_len = existing_preload ? strlen(existing_preload) : 0;
+       size_t total_len = existing_preload_len;
        const struct keyval *env;
+       size_t i;
 
        for (i = 0; i < _TC_LAST; i++) {
-               const char *ldpreload;
-               size_t ldpreloadlen;
-               char *tmp;
-
                if (t->config[i] == NULL)
                        continue;
 
-               ldpreload = env_config[i].ldpreload;
-               ldpreloadlen = strlen(ldpreload);
-               tmp = realloc(preload, preloadlen + 2 + ldpreloadlen);
-               if (tmp == NULL) {
+               /* Don't worry if we overallocate one strlen(" ") too many. */
+               total_len += strlen(" ") + strlen(env_config[i].ldpreload);
+       }
+
+       /* Do nothing, if we have no local ldpreload. */
+       if (total_len && total_len != existing_preload_len) {
+               char *preload;
+               size_t len = 0;
+
+               preload = malloc(total_len + sizeof(char));
+               if (preload == NULL) {
                        ERR("oom: test_export_environ()\n");
                        return;
                }
-               preload = tmp;
 
-               if (preloadlen > 0)
-                       preload[preloadlen++] = ' ';
-               memcpy(preload + preloadlen, ldpreload, ldpreloadlen);
-               preloadlen += ldpreloadlen;
-               preload[preloadlen] = '\0';
-       }
+               memcpy(preload, existing_preload, existing_preload_len);
+               len += existing_preload_len;
 
-       if (preload != NULL) {
-               const char *existing_preload = getenv("LD_PRELOAD");
-               if (existing_preload) {
-                       char *tmp;
-                       size_t len = strlen(existing_preload);
+               for (i = 0; i < _TC_LAST; i++) {
+                       const char *ldpreload;
+                       size_t ldpreloadlen;
 
-                       tmp = malloc(preloadlen + 2 + len);
-                       if (tmp == NULL) {
-                               ERR("oom: test_export_environ()\n");
-                               return;
-                       }
-                       memcpy(tmp, existing_preload, len);
-                       tmp[len++] = ' ';
-                       memcpy(tmp + len, preload, preloadlen);
-                       preloadlen += len;
-                       tmp[preloadlen] = '\0';
-                       free(preload);
-                       preload = tmp;
+                       if (t->config[i] == NULL)
+                               continue;
+
+                       ldpreload = env_config[i].ldpreload;
+                       ldpreloadlen = strlen(ldpreload);
+
+                       preload[len++] = ' ';
+                       memcpy(preload + len, ldpreload, ldpreloadlen);
+                       len += ldpreloadlen;
                }
+               preload[len] = '\0';
+
                setenv("LD_PRELOAD", preload, 1);
+               free(preload);
        }
 
        for (i = 0; i < _TC_LAST; i++) {