Add core:c/libc tests

core/c/libc/tests/general.odin

@@ -0,0 +1,50 @@
+package libc_tests
+
+import "core:c/libc"
+
+test_stdio :: proc() {
+    c: libc.char = 'C';
+    libc.puts("Hello from puts");
+    libc.printf("Hello from printf in %c\n", c);
+}
+test_thread :: proc() {
+    thread_proc :: proc "c" (rawptr) -> libc.int {
+        libc.printf("Hello from thread");
+        return 42;
+    }
+    thread: libc.thrd_t;
+    libc.thrd_create(&thread, thread_proc, nil);
+    result: libc.int;
+    libc.thrd_join(thread, &result);
+    libc.printf(" %d\n", result);
+}
+
+jmp: libc.jmp_buf;
+test_sjlj :: proc() {
+    if libc.setjmp(&jmp) != 0 {
+        libc.printf("Hello from longjmp\n");
+        return;
+    }
+    libc.printf("Hello from setjmp\n");
+    libc.longjmp(&jmp, 1);
+}
+test_signal :: proc() {
+    handler :: proc "c" (sig: libc.int) {
+        libc.printf("Hello from signal handler\n");
+    }
+    libc.signal(libc.SIGABRT, handler);
+    libc.raise(libc.SIGABRT);
+}
+test_atexit :: proc() {
+    handler :: proc "c" () {
+        libc.printf("Hello from atexit\n");
+    }
+    libc.atexit(handler);
+}
+main :: proc() {
+    test_stdio();
+    test_thread();
+    test_sjlj();
+    test_signal();
+    test_atexit();
+}