Informational 18 Bitcoin Committed Aug 14, 2025 · 08:23 UTC

common/json_parse_simple: make convenience functions inline

9112c1d5 View source ↗

Public commit record

What the developer wrote

Authored by Matt Whitlock

85/100 · Strong

common/json_parse_simple: make convenience functions inline

json_tok_streq(…) and json_get_member(…) are convenience wrappers for
json_tok_strneq(…) and json_get_membern(…) respectively. Unfortunately, using
them incurs a performance penalty in the common case where they are called with
a string literal argument because the compiler is unable to substitute a
compile-time constant in place of the buried call to strlen(…).

For example,

json_get_member(buf, tok, "example");

…will have worse performance than…

json_get_membern(buf, tok, "example", strlen("example"));

…because the former is forced to scan over "example" at run-time to count its
length whereas the latter is able to elide the strlen(…) call at compile time.

Hoist these convenience functions up into common/json_parse_simple.h and mark
them as inline so that the compiler can elide the strlen(…) call in the common
case of calling these functions with a string literal argument.

Changelog-None

✓ Specific, descriptive subject✓ Names a concrete action or component✓ Provides detailed explanatory context✓ Explains rationale or failure mode

The short version

What changed, and why it matters

This change moves two helper functions from a source file into a header file and marks them 'inline' so the compiler can optimize common calls. It is a performance cleanup, not a security fix. The functions behave the same way as before; only how the compiler sees them changes. Test stub files are updated to match the new internal layout.

Recommended action

No security action required; treat as a routine performance/refactoring commit.

Security signals we found

No strong security signals were identified.

Technical analysis

Evidence from the diff

The commit hoists json_tok_streq() and json_get_member() from common/json_parse_simple.c into common/json_parse_simple.h as static inline wrappers around json_tok_strneq() and json_get_membern(). The goal is to let the compiler constant-fold strlen() when these helpers are called with string literals. The implementations are unchanged; only linkage and visibility to the optimizer differ. Corresponding generated test stubs are switched from the old non-inline symbols to the underlying strneq/membern symbols. No behavioral or API change is introduced.

Changed components

common/json_parse_simple.ccommon/json_parse_simple.hplugins/bkpr/test/run-bkpr_db.cplugins/bkpr/test/run-recorder.cplugins/test/run-route-calc.cplugins/test/run-route-overlong.cwallet/test/run-wallet.c

Inspect captured patch +58 / −51

diff --git a/common/json_parse_simple.c b/common/json_parse_simple.c
index 7f9c630e..a40cb02f 100644
--- a/common/json_parse_simple.c
+++ b/common/json_parse_simple.c
@@ -33,11 +33,6 @@ bool json_tok_strneq(const char *buffer, const jsmntok_t *tok,
 	return memeq(buffer + tok->start, tok->end - tok->start, str, len);
 }
 
-bool json_tok_streq(const char *buffer, const jsmntok_t *tok, const char *str)
-{
-	return json_tok_strneq(buffer, tok, str, strlen(str));
-}
-
 bool json_tok_startswith(const char *buffer, const jsmntok_t *tok,
 			 const char *prefix)
 {
@@ -217,12 +212,6 @@ const jsmntok_t *json_get_membern(const char *buffer,
 	return NULL;
 }
 
-const jsmntok_t *json_get_member(const char *buffer, const jsmntok_t tok[],
-				 const char *label)
-{
-	return json_get_membern(buffer, tok, label, strlen(label));
-}
-
 const jsmntok_t *json_get_arr(const jsmntok_t tok[], size_t index)
 {
 	const jsmntok_t *t;
diff --git a/common/json_parse_simple.h b/common/json_parse_simple.h
index 710520d6..eb7a70d5 100644
--- a/common/json_parse_simple.h
+++ b/common/json_parse_simple.h
@@ -14,13 +14,17 @@ const char *json_tok_full(const char *buffer, const jsmntok_t *t);
 /* Include " if it's a string. */
 int json_tok_full_len(const jsmntok_t *t);
 
-/* Is this a string equal to str? */
-bool json_tok_streq(const char *buffer, const jsmntok_t *tok, const char *str);
-
 /* Is this a string equal to str of length len? */
 bool json_tok_strneq(const char *buffer, const jsmntok_t *tok,
 		     const char *str, size_t len);
 
+/* Is this a string equal to str? */
+static inline bool json_tok_streq(const char *buffer, const jsmntok_t *tok,
+				  const char *str)
+{
+	return json_tok_strneq(buffer, tok, str, strlen(str));
+}
+
 /* Does this string token start with prefix? */
 bool json_tok_startswith(const char *buffer, const jsmntok_t *tok,
 			 const char *prefix);
@@ -66,8 +70,12 @@ const jsmntok_t *json_get_membern(const char *buffer,
 				  const char *label, size_t len);
 
 /* Get top-level member. */
-const jsmntok_t *json_get_member(const char *buffer, const jsmntok_t tok[],
-				 const char *label);
+static inline const jsmntok_t *json_get_member(const char *buffer,
+					       const jsmntok_t tok[],
+					       const char *label)
+{
+	return json_get_membern(buffer, tok, label, strlen(label));
+}
 
 /* Get index'th array member. */
 const jsmntok_t *json_get_arr(const jsmntok_t tok[], size_t index);
diff --git a/plugins/bkpr/test/run-bkpr_db.c b/plugins/bkpr/test/run-bkpr_db.c
index 10ba59ae..13801dca 100644
--- a/plugins/bkpr/test/run-bkpr_db.c
+++ b/plugins/bkpr/test/run-bkpr_db.c
@@ -112,10 +112,11 @@ bool is_asterix_notification(const char *notification_name UNNEEDED,
 const char *json_get_id(const tal_t *ctx UNNEEDED,
 			const char *buffer UNNEEDED, const jsmntok_t *obj UNNEEDED)
 { fprintf(stderr, "json_get_id called!\n"); abort(); }
-/* Generated stub for json_get_member */
-const jsmntok_t *json_get_member(const char *buffer UNNEEDED, const jsmntok_t tok[] UNNEEDED,
-				 const char *label UNNEEDED)
-{ fprintf(stderr, "json_get_member called!\n"); abort(); }
+/* Generated stub for json_get_membern */
+const jsmntok_t *json_get_membern(const char *buffer UNNEEDED,
+				  const jsmntok_t tok[] UNNEEDED,
+				  const char *label UNNEEDED, size_t len UNNEEDED)
+{ fprintf(stderr, "json_get_membern called!\n"); abort(); }
 /* Generated stub for json_next */
 const jsmntok_t *json_next(const jsmntok_t *tok UNNEEDED)
 { fprintf(stderr, "json_next called!\n"); abort(); }
@@ -194,9 +195,10 @@ int json_tok_full_len(const jsmntok_t *t UNNEEDED)
 void json_tok_remove(jsmntok_t **tokens UNNEEDED,
 		     jsmntok_t *obj_or_array UNNEEDED, const jsmntok_t *tok UNNEEDED, size_t num UNNEEDED)
 { fprintf(stderr, "json_tok_remove called!\n"); abort(); }
-/* Generated stub for json_tok_streq */
-bool json_tok_streq(const char *buffer UNNEEDED, const jsmntok_t *tok UNNEEDED, const char *str UNNEEDED)
-{ fprintf(stderr, "json_tok_streq called!\n"); abort(); }
+/* Generated stub for json_tok_strneq */
+bool json_tok_strneq(const char *buffer UNNEEDED, const jsmntok_t *tok UNNEEDED,
+		     const char *str UNNEEDED, size_t len UNNEEDED)
+{ fprintf(stderr, "json_tok_strneq called!\n"); abort(); }
 /* Generated stub for last_fee_state */
 enum htlc_state last_fee_state(enum side opener UNNEEDED)
 { fprintf(stderr, "last_fee_state called!\n"); abort(); }
diff --git a/plugins/bkpr/test/run-recorder.c b/plugins/bkpr/test/run-recorder.c
index 16cd8e9b..351d4d26 100644
--- a/plugins/bkpr/test/run-recorder.c
+++ b/plugins/bkpr/test/run-recorder.c
@@ -118,10 +118,11 @@ bool is_asterix_notification(const char *notification_name UNNEEDED,
 const char *json_get_id(const tal_t *ctx UNNEEDED,
 			const char *buffer UNNEEDED, const jsmntok_t *obj UNNEEDED)
 { fprintf(stderr, "json_get_id called!\n"); abort(); }
-/* Generated stub for json_get_member */
-const jsmntok_t *json_get_member(const char *buffer UNNEEDED, const jsmntok_t tok[] UNNEEDED,
-				 const char *label UNNEEDED)
-{ fprintf(stderr, "json_get_member called!\n"); abort(); }
+/* Generated stub for json_get_membern */
+const jsmntok_t *json_get_membern(const char *buffer UNNEEDED,
+				  const jsmntok_t tok[] UNNEEDED,
+				  const char *label UNNEEDED, size_t len UNNEEDED)
+{ fprintf(stderr, "json_get_membern called!\n"); abort(); }
 /* Generated stub for json_next */
 const jsmntok_t *json_next(const jsmntok_t *tok UNNEEDED)
 { fprintf(stderr, "json_next called!\n"); abort(); }
@@ -200,9 +201,10 @@ int json_tok_full_len(const jsmntok_t *t UNNEEDED)
 void json_tok_remove(jsmntok_t **tokens UNNEEDED,
 		     jsmntok_t *obj_or_array UNNEEDED, const jsmntok_t *tok UNNEEDED, size_t num UNNEEDED)
 { fprintf(stderr, "json_tok_remove called!\n"); abort(); }
-/* Generated stub for json_tok_streq */
-bool json_tok_streq(const char *buffer UNNEEDED, const jsmntok_t *tok UNNEEDED, const char *str UNNEEDED)
-{ fprintf(stderr, "json_tok_streq called!\n"); abort(); }
+/* Generated stub for json_tok_strneq */
+bool json_tok_strneq(const char *buffer UNNEEDED, const jsmntok_t *tok UNNEEDED,
+		     const char *str UNNEEDED, size_t len UNNEEDED)
+{ fprintf(stderr, "json_tok_strneq called!\n"); abort(); }
 /* Generated stub for last_fee_state */
 enum htlc_state last_fee_state(enum side opener UNNEEDED)
 { fprintf(stderr, "last_fee_state called!\n"); abort(); }
diff --git a/plugins/test/run-route-calc.c b/plugins/test/run-route-calc.c
index 3898c3f4..73e56ce3 100644
--- a/plugins/test/run-route-calc.c
+++ b/plugins/test/run-route-calc.c
@@ -160,10 +160,11 @@ void json_array_end(struct json_stream *js UNNEEDED)
 /* Generated stub for json_array_start */
 void json_array_start(struct json_stream *js UNNEEDED, const char *fieldname UNNEEDED)
 { fprintf(stderr, "json_array_start called!\n"); abort(); }
-/* Generated stub for json_get_member */
-const jsmntok_t *json_get_member(const char *buffer UNNEEDED, const jsmntok_t tok[] UNNEEDED,
-				 const char *label UNNEEDED)
-{ fprintf(stderr, "json_get_member called!\n"); abort(); }
+/* Generated stub for json_get_membern */
+const jsmntok_t *json_get_membern(const char *buffer UNNEEDED,
+				  const jsmntok_t tok[] UNNEEDED,
+				  const char *label UNNEEDED, size_t len UNNEEDED)
+{ fprintf(stderr, "json_get_membern called!\n"); abort(); }
 /* Generated stub for json_next */
 const jsmntok_t *json_next(const jsmntok_t *tok UNNEEDED)
 { fprintf(stderr, "json_next called!\n"); abort(); }
@@ -245,9 +246,10 @@ const char *json_tok_full(const char *buffer UNNEEDED, const jsmntok_t *t UNNEED
 /* Generated stub for json_tok_full_len */
 int json_tok_full_len(const jsmntok_t *t UNNEEDED)
 { fprintf(stderr, "json_tok_full_len called!\n"); abort(); }
-/* Generated stub for json_tok_streq */
-bool json_tok_streq(const char *buffer UNNEEDED, const jsmntok_t *tok UNNEEDED, const char *str UNNEEDED)
-{ fprintf(stderr, "json_tok_streq called!\n"); abort(); }
+/* Generated stub for json_tok_strneq */
+bool json_tok_strneq(const char *buffer UNNEEDED, const jsmntok_t *tok UNNEEDED,
+		     const char *str UNNEEDED, size_t len UNNEEDED)
+{ fprintf(stderr, "json_tok_strneq called!\n"); abort(); }
 /* Generated stub for jsonrpc_request_start_ */
 struct out_req *jsonrpc_request_start_(struct command *cmd UNNEEDED,
 				       const char *method UNNEEDED,
diff --git a/plugins/test/run-route-overlong.c b/plugins/test/run-route-overlong.c
index 3683c0dd..ad0a63ec 100644
--- a/plugins/test/run-route-overlong.c
+++ b/plugins/test/run-route-overlong.c
@@ -157,10 +157,11 @@ void json_array_end(struct json_stream *js UNNEEDED)
 /* Generated stub for json_array_start */
 void json_array_start(struct json_stream *js UNNEEDED, const char *fieldname UNNEEDED)
 { fprintf(stderr, "json_array_start called!\n"); abort(); }
-/* Generated stub for json_get_member */
-const jsmntok_t *json_get_member(const char *buffer UNNEEDED, const jsmntok_t tok[] UNNEEDED,
-				 const char *label UNNEEDED)
-{ fprintf(stderr, "json_get_member called!\n"); abort(); }
+/* Generated stub for json_get_membern */
+const jsmntok_t *json_get_membern(const char *buffer UNNEEDED,
+				  const jsmntok_t tok[] UNNEEDED,
+				  const char *label UNNEEDED, size_t len UNNEEDED)
+{ fprintf(stderr, "json_get_membern called!\n"); abort(); }
 /* Generated stub for json_next */
 const jsmntok_t *json_next(const jsmntok_t *tok UNNEEDED)
 { fprintf(stderr, "json_next called!\n"); abort(); }
@@ -242,9 +243,10 @@ const char *json_tok_full(const char *buffer UNNEEDED, const jsmntok_t *t UNNEED
 /* Generated stub for json_tok_full_len */
 int json_tok_full_len(const jsmntok_t *t UNNEEDED)
 { fprintf(stderr, "json_tok_full_len called!\n"); abort(); }
-/* Generated stub for json_tok_streq */
-bool json_tok_streq(const char *buffer UNNEEDED, const jsmntok_t *tok UNNEEDED, const char *str UNNEEDED)
-{ fprintf(stderr, "json_tok_streq called!\n"); abort(); }
+/* Generated stub for json_tok_strneq */
+bool json_tok_strneq(const char *buffer UNNEEDED, const jsmntok_t *tok UNNEEDED,
+		     const char *str UNNEEDED, size_t len UNNEEDED)
+{ fprintf(stderr, "json_tok_strneq called!\n"); abort(); }
 /* Generated stub for jsonrpc_request_start_ */
 struct out_req *jsonrpc_request_start_(struct command *cmd UNNEEDED,
 				       const char *method UNNEEDED,
diff --git a/wallet/test/run-wallet.c b/wallet/test/run-wallet.c
index b3279625..881828ae 100644
--- a/wallet/test/run-wallet.c
+++ b/wallet/test/run-wallet.c
@@ -579,10 +579,11 @@ void json_array_end(struct json_stream *js UNNEEDED)
 /* Generated stub for json_array_start */
 void json_array_start(struct json_stream *js UNNEEDED, const char *fieldname UNNEEDED)
 { fprintf(stderr, "json_array_start called!\n"); abort(); }
-/* Generated stub for json_get_member */
-const jsmntok_t *json_get_member(const char *buffer UNNEEDED, const jsmntok_t tok[] UNNEEDED,
-				 const char *label UNNEEDED)
-{ fprintf(stderr, "json_get_member called!\n"); abort(); }
+/* Generated stub for json_get_membern */
+const jsmntok_t *json_get_membern(const char *buffer UNNEEDED,
+				  const jsmntok_t tok[] UNNEEDED,
+				  const char *label UNNEEDED, size_t len UNNEEDED)
+{ fprintf(stderr, "json_get_membern called!\n"); abort(); }
 /* Generated stub for json_next */
 const jsmntok_t *json_next(const jsmntok_t *tok UNNEEDED)
 { fprintf(stderr, "json_next called!\n"); abort(); }
@@ -636,9 +637,10 @@ bool json_tok_channel_id(const char *buffer UNNEEDED, const jsmntok_t *tok UNNEE
 /* Generated stub for json_tok_full */
 const char *json_tok_full(const char *buffer UNNEEDED, const jsmntok_t *t UNNEEDED)
 { fprintf(stderr, "json_tok_full called!\n"); abort(); }
-/* Generated stub for json_tok_streq */
-bool json_tok_streq(const char *buffer UNNEEDED, const jsmntok_t *tok UNNEEDED, const char *str UNNEEDED)
-{ fprintf(stderr, "json_tok_streq called!\n"); abort(); }
+/* Generated stub for json_tok_strneq */
+bool json_tok_strneq(const char *buffer UNNEEDED, const jsmntok_t *tok UNNEEDED,
+		     const char *str UNNEEDED, size_t len UNNEEDED)
+{ fprintf(stderr, "json_tok_strneq called!\n"); abort(); }
 /* Generated stub for kill_uncommitted_channel */
 void kill_uncommitted_channel(struct uncommitted_channel *uc UNNEEDED,
 			      const char *why UNNEEDED)

Risk score

Why this scored 18/100

Our methodology →

Potential impact 0/30

Exploitability 0/25

Stealth signal 0/15

Affected reach 5/15

Confidence 9/10

Evidence quality 4/5

Human-validated context

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What the developer wrote

What changed, and why it matters

Security signals we found

Evidence from the diff

Changed components

Why this scored 18/100

Community notes

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