tests: replace fake_criterion_tests section with `__attribute__((co…

…nstructor))`s adding to a linked list, fixing the padding bug

* Fixes #473.

The previous way of appending `struct fake_criterion_test`s by putting them into a section
was buggy because extra padding was added between the elements in the section,
so iterating through them from `__{start,stop}_fake_criterion_tests` didn't work correctly.

This new way uses `__attribute__((constructor))` to add each `struct fake_criterion_test`
to a singly linked list. A singly linked list is used for simplicity,
though it does mean the tests are run in reverse order within a file,
but I don't really think the test order should matter, so this should be okay.

misc/test_runner/include/ia2_test_runner.h

@@ -17,13 +17,16 @@ typedef void (*ia2_test_fn)(void);
 #endif
 
 struct fake_criterion_test {
+  struct fake_criterion_test *next;
   const char *suite;
   const char *name;
   ia2_test_fn test;
   ia2_test_fn init;
   int exit_code;
 };
 
+extern struct fake_criterion_test *fake_criterion_tests;
+
 #define _STRINGIFY(a) #a
 #define STRINGIFY(a) _STRINGIFY(a)
 
@@ -33,15 +36,20 @@ struct fake_criterion_test {
  * that reference it like the RHS when initializing struct fake_criterion_test's test field. The
  * last line of this macro is the start of the test function's definition and should be followed by { }
  */
-#define Test(suite_, name_, ...)                                                                                                 \
-  IA2_BEGIN_NO_WRAP                                                                                                              \
-  void fake_criterion_##suite_##_##name_(void);                                                                                  \
-  IA2_END_NO_WRAP                                                                                                                \
-  __attribute__((__section__("fake_criterion_tests"))) struct fake_criterion_test fake_criterion_##suite_##_##name_##_##test = { \
-      .suite = STRINGIFY(suite_),                                                                                                \
-      .name = STRINGIFY(name_),                                                                                                  \
-      .test = fake_criterion_##suite_##_##name_,                                                                                 \
-      ##__VA_ARGS__};                                                                                                            \
+#define Test(suite_, name_, ...)                                                            \
+  IA2_BEGIN_NO_WRAP                                                                         \
+  void fake_criterion_##suite_##_##name_(void);                                             \
+  IA2_END_NO_WRAP                                                                           \
+  struct fake_criterion_test fake_criterion_##suite_##_##name_##_##test IA2_SHARED_DATA = { \
+      .next = NULL,                                                                         \
+      .suite = STRINGIFY(suite_),                                                           \
+      .name = STRINGIFY(name_),                                                             \
+      .test = fake_criterion_##suite_##_##name_,                                            \
+      ##__VA_ARGS__};                                                                       \
+  __attribute__((constructor)) void fake_criterion_add_##suite_##_##name_##_##test(void) {  \
+    fake_criterion_##suite_##_##name_##_##test.next = fake_criterion_tests;                 \
+    fake_criterion_tests = &fake_criterion_##suite_##_##name_##_##test;                     \
+  }                                                                                         \
   void fake_criterion_##suite_##_##name_(void)
 
 #define cr_log_info(f, ...) printf(f "\n", ##__VA_ARGS__)

misc/test_runner/test_runner.c

@@ -8,8 +8,7 @@
 #include <sys/wait.h>
 #include <unistd.h>
 
-extern struct fake_criterion_test __start_fake_criterion_tests;
-extern struct fake_criterion_test __stop_fake_criterion_tests;
+struct fake_criterion_test *fake_criterion_tests IA2_SHARED_DATA = NULL;
 
 /* This is shared data to allow checking for violations from different compartments */
 bool expect_fault IA2_SHARED_DATA = false;
@@ -83,12 +82,8 @@ int main() {
    * invocation of the Test macro
    */
   sigaction(SIGSEGV, &act, NULL);
-  struct fake_criterion_test *test_info = &__start_fake_criterion_tests;
-  for (; test_info < &__stop_fake_criterion_tests; test_info++) {
+  for (struct fake_criterion_test *test_info = fake_criterion_tests; test_info; test_info = test_info->next) {
     fprintf(stderr, "running suite '%s' test '%s'...\n", test_info->suite, test_info->name);
-    if (!test_info->test) {
-      break;
-    }
     pid_t pid = fork();
     bool in_child = pid == 0;
     if (in_child) {