Add fuzz testing corpus and build

fuzz.c

@@ -0,0 +1,88 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include "wl.h"
+
+#define MAX_INPUT_SIZE (64 * 1024)  // 64KB max input
+#define ARENA_SIZE (1 << 20)         // 1MB arena
+
+// Persistent mode: AFL will call this loop many times without restarting
+__AFL_FUZZ_INIT();
+
+int main(int argc, char **argv)
+{
+    // Allocate arena once (outside the AFL loop)
+    char *mem = malloc(ARENA_SIZE);
+    if (mem == NULL) {
+        fprintf(stderr, "Failed to allocate memory\n");
+        return -1;
+    }
+
+    // Buffer for input
+    unsigned char *buf = __AFL_FUZZ_TESTCASE_BUF;
+
+#ifdef __AFL_HAVE_MANUAL_CONTROL
+    __AFL_INIT();
+#endif
+
+    // AFL persistent mode: loop up to 1000 times per process
+    while (__AFL_LOOP(1000)) {
+        int len = __AFL_FUZZ_TESTCASE_LEN;
+        
+        // Limit input size
+        if (len > MAX_INPUT_SIZE) {
+            len = MAX_INPUT_SIZE;
+        }
+        
+        // Reset arena for each iteration
+        WL_Arena arena = { mem, ARENA_SIZE, 0 };
+        
+        // Initialize compiler
+        WL_Compiler *c = wl_compiler_init(&arena);
+        if (c == NULL) {
+            continue;  // Out of memory, skip this input
+        }
+        
+        // Try to compile the input
+        WL_AddResult res = wl_compiler_add(
+            c, 
+            (WL_String) { "", 0 },  // empty path
+            (WL_String) { (char*)buf, len }
+        );
+        
+        // If compilation succeeded, try to link
+        if (res.type == WL_ADD_LINK) {
+            WL_Program program;
+            int ret = wl_compiler_link(c, &program);
+            
+            // If linking succeeded, optionally execute (for deeper fuzzing)
+            if (ret == 0) {
+                WL_Runtime *rt = wl_runtime_init(&arena, program);
+                if (rt != NULL) {
+                    // Execute up to 1000 steps to avoid infinite loops
+                    for (int i = 0; i < 1000; i++) {
+                        WL_EvalResult eval_res = wl_runtime_eval(rt);
+                        
+                        if (eval_res.type == WL_EVAL_DONE || 
+                            eval_res.type == WL_EVAL_ERROR) {
+                            break;
+                        }
+                        
+                        // Handle syscalls/sysvars by pushing dummy values
+                        if (eval_res.type == WL_EVAL_SYSVAR) {
+                            wl_push_s64(rt, 42);
+                        } else if (eval_res.type == WL_EVAL_SYSCALL) {
+                            wl_push_s64(rt, 42);
+                        }
+                    }
+                }
+            }
+        }
+        
+        // Arena is automatically reset on next iteration
+    }
+
+    free(mem);
+    return 0;
+}