Merge branch 'jk/c23-const-preserving-fixes-more' into jch

Further work to adjust the codebase for C23 that changes functions
like strchr() that discarded constness when they return a pointer into
a const string to preserve constness.

* jk/c23-const-preserving-fixes-more:
  refs/files-backend: drop const to fix strchr() warning
  http: drop const to fix strstr() warning
  range-diff: drop const to fix strstr() warnings
  pkt-line: make packet_reader.line non-const
  skip_prefix(): check const match between in and out params
  pseudo-merge: fix disk reads from find_pseudo_merge()
  find_last_dir_sep(): convert inline function to macro
  run-command: explicitly cast away constness when assigning to void
  pager: explicitly cast away strchr() constness
  transport-helper: drop const to fix strchr() warnings
  http: add const to fix strchr() warnings
  convert: add const to fix strchr() warnings

Author: gitster

builtin/receive-pack.c

@@ -1029,8 +1029,8 @@ static int read_proc_receive_report(struct packet_reader *reader,
 
 	for (;;) {
 		struct object_id old_oid, new_oid;
-		const char *head;
-		const char *refname;
+		char *head;
+		char *refname;
 		char *p;
 		enum packet_read_status status;
 
@@ -1054,7 +1054,8 @@ static int read_proc_receive_report(struct packet_reader *reader,
 		}
 		*p++ = '\0';
 		if (!strcmp(head, "option")) {
-			const char *key, *val;
+			char *key;
+			const char *val;
 
 			if (!hint || !(report || new_report)) {
 				if (!once++)

convert.c

@@ -1168,7 +1168,8 @@ static int ident_to_worktree(const char *src, size_t len,
 			     struct strbuf *buf, int ident)
 {
 	struct object_id oid;
-	char *to_free = NULL, *dollar, *spc;
+	char *to_free = NULL;
+	const char *dollar, *spc;
 	int cnt;
 
 	if (!ident)

git-compat-util.h

@@ -335,11 +335,7 @@ static inline int is_path_owned_by_current_uid(const char *path,
 #endif
 
 #ifndef find_last_dir_sep
-static inline char *git_find_last_dir_sep(const char *path)
-{
-	return strrchr(path, '/');
-}
-#define find_last_dir_sep git_find_last_dir_sep
+#define find_last_dir_sep(path) strrchr((path), '/')
 #endif
 
 #ifndef has_dir_sep
@@ -495,6 +491,23 @@ static inline bool skip_prefix(const char *str, const char *prefix,
 	return false;
 }
 
+/*
+ * Check that an out-parameter that is "at least as const as" a matching
+ * in-parameter. For example, skip_prefix() will return "out" that is a subset
+ * of "str". So:
+ *
+ *  const str, const out: ok
+ *  non-const str, const out: ok
+ *  non-const str, non-const out: ok
+ *  const str, non-const out: compile error
+ *
+ *  See the skip_prefix macro below for an example of use.
+ */
+#define CONST_OUTPARAM(in, out) \
+    ((const char **)(0 ? ((*(out) = (in)),(out)) : (out)))
+#define skip_prefix(str, prefix, out) \
+	skip_prefix((str), (prefix), CONST_OUTPARAM((str), (out)))
+
 /*
  * Like skip_prefix, but promises never to read past "len" bytes of the input
  * buffer, and returns the remaining number of bytes in "out" via "outlen".
@@ -901,6 +914,9 @@ static inline bool skip_iprefix(const char *str, const char *prefix,
 	return false;
 }
 
+#define skip_iprefix(str, prefix, out) \
+	skip_iprefix((str), (prefix), CONST_OUTPARAM((str), (out)))
+
 /*
  * Like skip_prefix_mem, but compare case-insensitively. Note that the
  * comparison is done via tolower(), so it is strictly ASCII (no multi-byte

hex.c

@@ -54,9 +54,9 @@ int get_oid_hex(const char *hex, struct object_id *oid)
 	return get_oid_hex_algop(hex, oid, the_hash_algo);
 }
 
-int parse_oid_hex_algop(const char *hex, struct object_id *oid,
-			const char **end,
-			const struct git_hash_algo *algop)
+int parse_oid_hex_algop_impl(const char *hex, struct object_id *oid,
+			     const char **end,
+			     const struct git_hash_algo *algop)
 {
 	int ret = get_oid_hex_algop(hex, oid, algop);
 	if (!ret)

hex.h

@@ -40,8 +40,10 @@ char *oid_to_hex(const struct object_id *oid);						/* same static buffer */
  * other invalid character.  end is only updated on success; otherwise, it is
  * unmodified.
  */
-int parse_oid_hex_algop(const char *hex, struct object_id *oid, const char **end,
-			const struct git_hash_algo *algo);
+int parse_oid_hex_algop_impl(const char *hex, struct object_id *oid, const char **end,
+			     const struct git_hash_algo *algo);
+#define parse_oid_hex_algop(hex, oid, end, algo) \
+	parse_oid_hex_algop_impl((hex), (oid), CONST_OUTPARAM((hex), (end)), (algo))
 
 /*
  * These functions work like get_oid_hex and parse_oid_hex, but they will parse

http-push.c

@@ -99,7 +99,7 @@ static struct object_list *objects;
 
 struct repo {
 	char *url;
-	char *path;
+	const char *path;
 	int path_len;
 	int has_info_refs;
 	int can_update_info_refs;

http.c

@@ -748,7 +748,7 @@ static int has_proxy_cert_password(void)
 static int redact_sensitive_header(struct strbuf *header, size_t offset)
 {
 	int ret = 0;
-	const char *sensitive_header;
+	char *sensitive_header;
 
 	if (trace_curl_redact &&
 	    (skip_iprefix(header->buf + offset, "Authorization:", &sensitive_header) ||
@@ -765,7 +765,7 @@ static int redact_sensitive_header(struct strbuf *header, size_t offset)
 	} else if (trace_curl_redact &&
 		   skip_iprefix(header->buf + offset, "Cookie:", &sensitive_header)) {
 		struct strbuf redacted_header = STRBUF_INIT;
-		const char *cookie;
+		char *cookie;
 
 		while (isspace(*sensitive_header))
 			sensitive_header++;

pager.c

@@ -118,7 +118,8 @@ static void setup_pager_env(struct strvec *env)
 			split_cmdline_strerror(n));
 
 	for (i = 0; i < n; i++) {
-		char *cp = strchr(argv[i], '=');
+		/* we know this is writable because it was split from pager_env */
+		char *cp = strchr((char *)argv[i], '=');
 
 		if (!cp)
 			die("malformed build-time PAGER_ENV");

pkt-line.h

@@ -184,7 +184,7 @@ struct packet_reader {
 	int pktlen;
 
 	/* the last line read */
-	const char *line;
+	char *line;
 
 	/* indicates if a line has been peeked */
 	int line_peeked;

pseudo-merge.c

@@ -638,31 +638,37 @@ static int pseudo_merge_commit_cmp(const void *va, const void *vb)
 	return 0;
 }
 
-static struct pseudo_merge_commit *find_pseudo_merge(const struct pseudo_merge_map *pm,
-						     uint32_t pos)
+static int find_pseudo_merge(const struct pseudo_merge_map *pm, uint32_t pos,
+			     struct pseudo_merge_commit *out)
 {
+	const unsigned char *at;
+
 	if (!pm->commits_nr)
-		return NULL;
+		return 0;
 
-	return bsearch(&pos, pm->commits, pm->commits_nr,
-		       PSEUDO_MERGE_COMMIT_RAWSZ, pseudo_merge_commit_cmp);
+	at = bsearch(&pos, pm->commits, pm->commits_nr,
+		     PSEUDO_MERGE_COMMIT_RAWSZ, pseudo_merge_commit_cmp);
+	if (!at)
+		return 0;
+
+	read_pseudo_merge_commit_at(out, at);
+	return 1;
 }
 
 int apply_pseudo_merges_for_commit(const struct pseudo_merge_map *pm,
 				   struct bitmap *result,
 				   struct commit *commit, uint32_t commit_pos)
 {
 	struct pseudo_merge *merge;
-	struct pseudo_merge_commit *merge_commit;
+	struct pseudo_merge_commit merge_commit;
 	int ret = 0;
 
-	merge_commit = find_pseudo_merge(pm, commit_pos);
-	if (!merge_commit)
+	if (!find_pseudo_merge(pm, commit_pos, &merge_commit))
 		return 0;
 
-	if (merge_commit->pseudo_merge_ofs & ((uint64_t)1<<63)) {
+	if (merge_commit.pseudo_merge_ofs & ((uint64_t)1<<63)) {
 		struct pseudo_merge_commit_ext ext = { 0 };
-		off_t ofs = merge_commit->pseudo_merge_ofs & ~((uint64_t)1<<63);
+		off_t ofs = merge_commit.pseudo_merge_ofs & ~((uint64_t)1<<63);
 		uint32_t i;
 
 		if (pseudo_merge_ext_at(pm, &ext, ofs) < -1) {
@@ -673,11 +679,11 @@ int apply_pseudo_merges_for_commit(const struct pseudo_merge_map *pm,
 		}
 
 		for (i = 0; i < ext.nr; i++) {
-			if (nth_pseudo_merge_ext(pm, &ext, merge_commit, i) < 0)
+			if (nth_pseudo_merge_ext(pm, &ext, &merge_commit, i) < 0)
 				return ret;
 
 			merge = pseudo_merge_at(pm, &commit->object.oid,
-						merge_commit->pseudo_merge_ofs);
+						merge_commit.pseudo_merge_ofs);
 
 			if (!merge)
 				return ret;
@@ -687,7 +693,7 @@ int apply_pseudo_merges_for_commit(const struct pseudo_merge_map *pm,
 		}
 	} else {
 		merge = pseudo_merge_at(pm, &commit->object.oid,
-					merge_commit->pseudo_merge_ofs);
+					merge_commit.pseudo_merge_ofs);
 
 		if (!merge)
 			return ret;