Rewrite strnlen replacement implementation from 8a241792f9.

The previous placement of the fallback implementation in libpgcommon
was problematic, because libpqport functions need strnlen
functionality.

Move replacement into libpgport. Provide strnlen() under its posix
name, instead of pg_strnlen(). Fix stupid configure bug, executing the
test only when compiled with threading support.

Author: Andres Freund
Discussion: https://postgr.es/m/E1e1gR2-0005fB-SI@gemulon.postgresql.org

src/backend/utils/mmgr/mcxt.c

@@ -21,7 +21,6 @@
 
 #include "postgres.h"
 
-#include "common/string.h"
 #include "miscadmin.h"
 #include "utils/memdebug.h"
 #include "utils/memutils.h"
@@ -1089,7 +1088,7 @@ pnstrdup(const char *in, Size len)
 {
 	char	   *out;
 
-	len = pg_strnlen(in, len);
+	len = strnlen(in, len);
 
 	out = palloc(len + 1);
 	memcpy(out, in, len);

src/common/string.c

@@ -41,23 +41,3 @@ pg_str_endswith(const char *str, const char *end)
 	str += slen - elen;
 	return strcmp(str, end) == 0;
 }
-
-
-/*
- * Portable version of posix' strnlen.
- *
- * Returns the number of characters before a null-byte in the string pointed
- * to by str, unless there's no null-byte before maxlen. In the latter case
- * maxlen is returned.
- */
-#ifndef HAVE_STRNLEN
-size_t
-pg_strnlen(const char *str, size_t maxlen)
-{
-	const char *p = str;
-
-	while (maxlen-- > 0 && *p)
-		p++;
-	return p - str;
-}
-#endif

src/include/common/string.h

@@ -12,19 +12,4 @@
 
 extern bool pg_str_endswith(const char *str, const char *end);
 
-/*
- * Portable version of posix' strnlen.
- *
- * Returns the number of characters before a null-byte in the string pointed
- * to by str, unless there's no null-byte before maxlen. In the latter case
- * maxlen is returned.
- *
- * Use the system strnlen if provided, it's likely to be faster.
- */
-#ifdef HAVE_STRNLEN
-#define pg_strnlen(str, maxlen) strnlen(str, maxlen)
-#else
-extern size_t pg_strnlen(const char *str, size_t maxlen);
-#endif
-
 #endif							/* COMMON_STRING_H */

src/include/pg_config.h.in

@@ -147,6 +147,10 @@
    don't. */
 #undef HAVE_DECL_STRLCPY
 
+/* Define to 1 if you have the declaration of `strnlen', and to 0 if you
+   don't. */
+#undef HAVE_DECL_STRNLEN
+
 /* Define to 1 if you have the declaration of `sys_siglist', and to 0 if you
    don't. */
 #undef HAVE_DECL_SYS_SIGLIST

src/include/pg_config.h.win32

@@ -99,6 +99,10 @@
    don't. */
 #define HAVE_DECL_SNPRINTF 1
 
+/* Define to 1 if you have the declaration of `strnlen', and to 0 if you
+   don't. */
+#define HAVE_DECL_STRNLEN 1
+
 /* Define to 1 if you have the declaration of `vsnprintf', and to 0 if you
    don't. */
 #define HAVE_DECL_VSNPRINTF 1
@@ -255,6 +259,9 @@
 /* Define to 1 if you have the <pam/pam_appl.h> header file. */
 /* #undef HAVE_PAM_PAM_APPL_H */
 
+/* Define to 1 if you have the `strnlen' function. */
+#define HAVE_STRNLEN 1
+
 /* Define to 1 if you have the `poll' function. */
 /* #undef HAVE_POLL */
 
@@ -345,9 +352,6 @@
 /* Define to 1 if you have the <string.h> header file. */
 #define HAVE_STRING_H 1
 
-/* Define to 1 if you have the `strnlen' function. */
-#define HAVE_STRNLEN
-
 /* Define to use have a strong random number source */
 #define HAVE_STRONG_RANDOM 1
 

src/include/port.h

@@ -406,6 +406,10 @@ extern size_t strlcat(char *dst, const char *src, size_t siz);
 extern size_t strlcpy(char *dst, const char *src, size_t siz);
 #endif
 
+#if !HAVE_DECL_STRNLEN
+extern size_t strnlen(const char *str, size_t maxlen);
+#endif
+
 #if !defined(HAVE_RANDOM)
 extern long random(void);
 #endif

src/port/snprintf.c

@@ -43,8 +43,6 @@
 #endif
 #include <sys/param.h>
 
-#include "common/string.h"
-
 #ifndef NL_ARGMAX
 #define NL_ARGMAX 16
 #endif
@@ -804,7 +802,7 @@ fmtstr(char *value, int leftjust, int minlen, int maxwidth,
 	 * than that.
 	 */
 	if (pointflag)
-		vallen = pg_strnlen(value, maxwidth);
+		vallen = strnlen(value, maxwidth);
 	else
 		vallen = strlen(value);
 

src/port/strnlen.c

@@ -0,0 +1,33 @@
+/*-------------------------------------------------------------------------
+ *
+ * strnlen.c
+ *		Fallback implementation of strnlen().
+ *
+ *
+ * Portions Copyright (c) 1996-2017, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ * IDENTIFICATION
+ *	  src/port/strnlen.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "c.h"
+
+/*
+ * Implementation of posix' strnlen for systems where it's not available.
+ *
+ * Returns the number of characters before a null-byte in the string pointed
+ * to by str, unless there's no null-byte before maxlen. In the latter case
+ * maxlen is returned.
+ */
+size_t
+strnlen(const char *str, size_t maxlen)
+{
+	const char *p = str;
+
+	while (maxlen-- > 0 && *p)
+		p++;
+	return p - str;
+}