From 25a07c30e5e19f13c32c7ab561391aefa38bc33d Mon Sep 17 00:00:00 2001
From: Paul Eggert <eggert@cs.ucla.edu>
Date: Wed, 20 May 2026 19:22:37 -0700
Subject: Don’t use VLA in etags.c mercury_decl
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* lib-src/etags.c (mercury_decl): Don’t use a VLA,
as C11+ says VLAs are optional.  Instead, redo to
omit the need for an array at all.
---
 lib-src/etags.c | 38 ++++++++++++++++++++------------------
 1 file changed, 20 insertions(+), 18 deletions(-)

(limited to 'lib-src')

diff --git a/lib-src/etags.c b/lib-src/etags.c
index f218dba2902..4114ba6b655 100644
--- a/lib-src/etags.c
+++ b/lib-src/etags.c
@@ -6654,6 +6654,14 @@ static const char *Mercury_decl_tags[] = {"type", "solver type", "pred",
   "initialise", "finalise", "mutable", "module", "interface", "implementation",
   "import_module", "use_module", "include_module", "end_module", "some", "all"};
 
+/* Return true if array of char BUF, of length LEN, equals STR.  */
+
+static bool
+memstreq (char const *buf, ptrdiff_t len, char const *str)
+{
+  return strlen (str) == len && memeq (buf, str, len);
+}
+
 static mercury_pos_t
 mercury_decl (char *s, size_t pos)
 {
@@ -6661,27 +6669,24 @@ mercury_decl (char *s, size_t pos)
 
   if (s == NULL) return null_pos;
 
-  size_t origpos;
-  origpos = pos;
+  size_t origpos = pos;
+  char *decl_type = s + origpos;
 
   while (c_isalnum (s[pos]) || s[pos] == '_')
     pos++;
 
-  unsigned char decl_type_length = pos - origpos;
-  char buf[decl_type_length + 1];
-  memset (buf, 0, decl_type_length + 1);
+  ptrdiff_t decl_type_length = pos - origpos;
 
   /* Mercury declaration tags.  Consume them, then check the declaration item
      following :- is legitimate, then go on as in the prolog case.  */
 
-  memcpy (buf, &s[origpos], decl_type_length);
-
   bool found_decl_tag = false;
 
   if (is_mercury_quantifier)
     {
-      if (strcmp (buf, "pred") != 0 && strcmp (buf, "func") != 0) /* Bad syntax.  */
-	return null_pos;
+      if (! (memstreq (decl_type, decl_type_length, "pred")
+	     || memstreq (decl_type, decl_type_length, "func")))
+	return null_pos; /* Bad syntax.  */
 
       is_mercury_quantifier = false; /* Reset to base value.  */
       found_decl_tag = true;
@@ -6690,14 +6695,14 @@ mercury_decl (char *s, size_t pos)
     {
       for (int j = 0; j < sizeof (Mercury_decl_tags) / sizeof (char*); ++j)
 	{
-	  if (strcmp (buf, Mercury_decl_tags[j]) == 0)
+	  if (memstreq (decl_type, decl_type_length, Mercury_decl_tags[j]))
 	    {
 	      found_decl_tag = true;
-	      if (strcmp (buf, "type") == 0)
+	      if (memstreq (decl_type, decl_type_length, "type"))
 		is_mercury_type = true;
 
-	      if (strcmp (buf, "some") == 0
-		  || strcmp (buf, "all") == 0)
+	      if (memstreq (decl_type, decl_type_length, "some")
+		  || memstreq (decl_type, decl_type_length, "all"))
 		{
 		  is_mercury_quantifier = true;
 		}
@@ -6707,18 +6712,15 @@ mercury_decl (char *s, size_t pos)
 	  else
 	    /* 'solver type' has a blank in the middle,
 	       so this is the hard case.  */
-	    if (strcmp (buf, "solver") == 0)
+	    if (memstreq (decl_type, decl_type_length, "solver"))
 	      {
 		do
 		  pos++;
 		while (c_isalnum (s[pos]) || s[pos] == '_');
 
 		decl_type_length = pos - origpos;
-		char buf2[decl_type_length + 1];
-		memset (buf2, 0, decl_type_length + 1);
-		memcpy (buf2, &s[origpos], decl_type_length);
 
-		if (strcmp (buf2, "solver type") == 0)
+		if (memstreq (decl_type, decl_type_length, "solver type"))
 		  {
 		    found_decl_tag = false;
 		    break;  /* Found declaration tag of rank j.  */
-- 
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