Merge bitcoin-core/secp256k1#1865: test: enable -Wunused-function in test suite (Fix #1831)

a77dacad9a test: enable -Wunused-function in test suite (Fix #1831) (kallal79)

Pull request description:

  This PR addresses issue #1831 by enabling the `-Wunused-function` compiler warning within the test suite.

  Currently, `-Wno-unused-function` is passed globally to disable warnings about unused functions, making it too easy to write a test case but forget to actually call it. To catch untested helper functions safely, this PR uses GCC/Clang pragmas scoped strictly to the body of the test files.

  ### Changes Made:
  - Added `#pragma GCC diagnostic warning "-Wunused-function"` directly after the `#include` statements in `src/tests.c`, `src/tests_exhaustive.c`, `src/ctime_tests.c`, and `src/unit_test.c`.
  Fixes #1831

ACKs for top commit:
  real-or-random:
    ACK a77dacad9a
  hebasto:
    ACK a77dacad9a.

Tree-SHA512: 775d633d9d2e95154b6718270ce1687a1b20c2c8cc67c909953b3395d76e6853e6be1d6a95d8aef3f15a78dec3497bea8e3864e36830977e11beb42ea9abcc31

src/ctime_tests.c

@@ -40,6 +40,11 @@
 #include "../include/secp256k1_ellswift.h"
 #endif
 
+#if defined(__GNUC__)
+# pragma GCC diagnostic push
+# pragma GCC diagnostic warning "-Wunused-function"
+#endif
+
 static void run_tests(secp256k1_context *ctx, unsigned char *key);
 
 int main(void) {
@@ -265,3 +270,7 @@ static void run_tests(secp256k1_context *ctx, unsigned char *key) {
 
 #endif
 }
+
+#if defined(__GNUC__)
+# pragma GCC diagnostic pop
+#endif

src/tests.c

@@ -37,6 +37,11 @@
 #include "int128_impl.h"
 #endif
 
+#if defined(__GNUC__)
+# pragma GCC diagnostic push
+# pragma GCC diagnostic warning "-Wunused-function"
+#endif
+
 #define CONDITIONAL_TEST(cnt, nam) if (COUNT < (cnt)) { printf("Skipping %s (iteration count too low)\n", nam); } else
 
 static secp256k1_context *CTX = NULL;
@@ -8091,3 +8096,7 @@ int main(int argc, char **argv) {
     if (tf_init(&tf, argc, argv) != 0) return EXIT_FAILURE;
     return tf_run(&tf);
 }
+
+#if defined(__GNUC__)
+# pragma GCC diagnostic pop
+#endif

src/tests_exhaustive.c

@@ -31,6 +31,11 @@
 #include "testutil.h"
 #include "util.h"
 
+#if defined(__GNUC__)
+# pragma GCC diagnostic push
+# pragma GCC diagnostic warning "-Wunused-function"
+#endif
+
 static int count = 2;
 
 static uint32_t num_cores = 1;
@@ -467,3 +472,7 @@ int main(int argc, char** argv) {
     printf("no problems found\n");
     return EXIT_SUCCESS;
 }
+
+#if defined(__GNUC__)
+# pragma GCC diagnostic pop
+#endif

src/unit_test.c

@@ -17,6 +17,11 @@
 #include "testrand.h"
 #include "tests_common.h"
 
+#if defined(__GNUC__)
+# pragma GCC diagnostic push
+# pragma GCC diagnostic warning "-Wunused-function"
+#endif
+
 #define UNUSED(x) (void)(x)
 
 /* Number of times certain tests will run */
@@ -477,3 +482,7 @@ static int tf_run(struct tf_framework* tf) {
 
     return status;
 }
+
+#if defined(__GNUC__)
+# pragma GCC diagnostic pop
+#endif