From 09c0fb72ca2fa45999f690c7b5e88e7fc73ad1c7 Mon Sep 17 00:00:00 2001
From: Andrew Noyes <andrew@weaselab.dev>
Date: Wed, 15 Jul 2026 12:30:05 -0400
Subject: [PATCH] Handle null parser in WeaselJsonParser_parse

Closes #51
---
 include/weaseljson.h | 2 ++
 src/lib.cpp          | 3 +++
 src/test.cpp         | 5 +++++
 src/validate.cpp     | 3 +++
 4 files changed, 13 insertions(+)

diff --git a/include/weaseljson.h b/include/weaseljson.h
index 4a42681..211dd1b 100644
--- a/include/weaseljson.h
+++ b/include/weaseljson.h
@@ -38,6 +38,8 @@ enum WeaselJsonStatus {
   WeaselJson_REJECT,
   /** json is too deeply nested */
   WeaselJson_OVERFLOW,
+  /** Tried to call parse on a null parser */
+  WeaselJson_NULL,
 };
 
 typedef struct WeaselJsonParser WeaselJsonParser;
diff --git a/src/lib.cpp b/src/lib.cpp
index 715f2c6..b805e01 100644
--- a/src/lib.cpp
+++ b/src/lib.cpp
@@ -46,6 +46,9 @@ WeaselJsonParser_destroy(WeaselJsonParser *parser) {
 
 __attribute__((visibility("default"))) WeaselJsonStatus
 WeaselJsonParser_parse(WeaselJsonParser *parser, char *buf, int len) {
+  if (parser == nullptr) [[unlikely]] {
+    return WeaselJson_NULL;
+  }
   return ((Parser3 *)parser)->parse(buf, len);
 }
 }
diff --git a/src/test.cpp b/src/test.cpp
index 6fef3a7..0c63161 100644
--- a/src/test.cpp
+++ b/src/test.cpp
@@ -330,6 +330,11 @@ TEST_CASE("parse rejects negative length") {
   WeaselJsonParser_destroy(parser);
 }
 
+TEST_CASE("Calling parse with nullptr doesn't crash") {
+  char buf[10] = "hello";
+  REQUIRE(WeaselJsonParser_parse(nullptr, buf, -1) == WeaselJson_NULL);
+}
+
 TEST_CASE("streaming") { testStreaming(json); }
 
 TEST_CASE("reset clears inKey and transient state") {
diff --git a/src/validate.cpp b/src/validate.cpp
index abbd2fa..f8d1adc 100644
--- a/src/validate.cpp
+++ b/src/validate.cpp
@@ -33,6 +33,9 @@ int main(int argc, char **argv) {
     case WeaselJson_REJECT:
     case WeaselJson_OVERFLOW:
       return 1;
+    case WeaselJson_NULL:
+      fprintf(stderr, "Could not create parser\n");
+      return 1;
     }
     if (l == 0) {
       return 1;