test memory limit

example/mem-limit/mem.jdg

@@ -0,0 +1,35 @@
+// End-to-end check that memory_limit is actually enforced by the runner.
+// The solution allocates N MiB (argv[1]) and touches every page.
+//
+//   - "within_limit" allocates 16 MiB under a 256 MiB cap → expected PASS
+//   - "exceeds_limit" allocates 256 MiB under a 64 MiB cap → expected MLE
+//
+// The workflow runs judge --json and asserts these statuses via jq.
+
+build         "$CC -O2 -std=c11 -Wall -Wextra solution.c -o solution"
+build_windows "if /I \"%CC%\"==\"msvc\" (cl /nologo /O2 /W3 solution.c /Fe:solution.exe) else (%CC% -O2 -std=c11 -Wall -Wextra solution.c -o solution.exe)"
+
+binary = "solution"
+timeout 10s
+
+normalize_crlf = true
+
+group("within_limit") {
+    weight = 1.0
+    memory_limit = 256M
+
+    test("allocate_16mb") {
+        args   = ["16"]
+        stdout = "ok 16\n"
+    }
+}
+
+group("exceeds_limit") {
+    weight = 0.0  // score doesn't matter — we assert the status in CI
+    memory_limit = 64M
+
+    test("allocate_256mb") {
+        args = ["256"]
+        // no stdout matcher: process is expected to be killed before it prints
+    }
+}

example/mem-limit/solution.c

@@ -0,0 +1,27 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+int main(int argc, char **argv) {
+    if (argc < 2) {
+        fprintf(stderr, "usage: %s <megabytes>\n", argv[0]);
+        return 1;
+    }
+    long mb = strtol(argv[1], NULL, 10);
+    if (mb <= 0) return 1;
+
+    size_t bytes = (size_t)mb * 1024 * 1024;
+    char *p = (char *)malloc(bytes);
+    if (!p) {
+        fprintf(stderr, "malloc failed\n");
+        return 2;
+    }
+    for (size_t i = 0; i < bytes; i += 4096) {
+        p[i] = (char)(i & 0xff);
+    }
+    volatile char sink = p[bytes - 1];
+    (void)sink;
+
+    printf("ok %ld\n", mb);
+    return 0;
+}