Support use of strnlen() in pre-v11 branches.

Back-patch a minimal subset of commits fffd651e8 and 46912d9b1,
to support strnlen() on all platforms without adding any callers.
This will be needed by a following bug fix.

configure

@@ -13513,6 +13513,16 @@ fi
 cat >>confdefs.h <<_ACEOF
 #define HAVE_DECL_STRLCPY $ac_have_decl
 _ACEOF
+ac_fn_c_check_decl "$LINENO" "strnlen" "ac_cv_have_decl_strnlen" "$ac_includes_default"
+if test "x$ac_cv_have_decl_strnlen" = xyes; then :
+  ac_have_decl=1
+else
+  ac_have_decl=0
+fi
+
+cat >>confdefs.h <<_ACEOF
+#define HAVE_DECL_STRNLEN $ac_have_decl
+_ACEOF
 
 # This is probably only present on macOS, but may as well check always
 ac_fn_c_check_decl "$LINENO" "F_FULLFSYNC" "ac_cv_have_decl_F_FULLFSYNC" "#include <fcntl.h>
@@ -13880,6 +13890,19 @@ esac
 
 fi
 
+ac_fn_c_check_func "$LINENO" "strnlen" "ac_cv_func_strnlen"
+if test "x$ac_cv_func_strnlen" = xyes; then :
+  $as_echo "#define HAVE_STRNLEN 1" >>confdefs.h
+
+else
+  case " $LIBOBJS " in
+  *" strnlen.$ac_objext "* ) ;;
+  *) LIBOBJS="$LIBOBJS strnlen.$ac_objext"
+ ;;
+esac
+
+fi
+
 
 
 case $host_os in

configure.in

@@ -1548,7 +1548,7 @@ AC_CHECK_DECLS(posix_fadvise, [], [], [#include <fcntl.h>])
 ]) # fi
 
 AC_CHECK_DECLS(fdatasync, [], [], [#include <unistd.h>])
-AC_CHECK_DECLS([strlcat, strlcpy])
+AC_CHECK_DECLS([strlcat, strlcpy, strnlen])
 # This is probably only present on macOS, but may as well check always
 AC_CHECK_DECLS(F_FULLFSYNC, [], [], [#include <fcntl.h>])
 
@@ -1640,7 +1640,7 @@ else
   AC_CHECK_FUNCS([fpclass fp_class fp_class_d class], [break])
 fi
 
-AC_REPLACE_FUNCS([crypt fls getopt getrusage inet_aton mkdtemp random rint srandom strerror strlcat strlcpy])
+AC_REPLACE_FUNCS([crypt fls getopt getrusage inet_aton mkdtemp random rint srandom strerror strlcat strlcpy strnlen])
 
 case $host_os in
 

src/include/pg_config.h.in

@@ -150,6 +150,10 @@
    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 `strtoll', and to 0 if you
    don't. */
 #undef HAVE_DECL_STRTOLL
@@ -504,6 +508,9 @@
 /* Define to 1 if you have the `strlcpy' function. */
 #undef HAVE_STRLCPY
 
+/* Define to 1 if you have the `strnlen' function. */
+#undef HAVE_STRNLEN
+
 /* Define to use have a strong random number source */
 #undef HAVE_STRONG_RANDOM
 

src/include/pg_config.h.win32

@@ -102,6 +102,10 @@
    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 `strtoll', and to 0 if you
    don't. */
 #define HAVE_DECL_STRTOLL 1
@@ -271,6 +275,9 @@
 /* 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 */
 

src/include/port.h

@@ -409,6 +409,10 @@ 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/interfaces/libpq/.gitignore

@@ -18,6 +18,7 @@
 /snprintf.c
 /strerror.c
 /strlcpy.c
+/strnlen.c
 /thread.c
 /win32error.c
 /win32setlocale.c

src/interfaces/libpq/Makefile

@@ -38,7 +38,7 @@ OBJS=	fe-auth.o fe-auth-scram.o fe-connect.o fe-exec.o fe-misc.o fe-print.o fe-l
 OBJS += chklocale.o inet_net_ntop.o noblock.o pgstrcasecmp.o pqsignal.o \
 	thread.o
 # libpgport C files that are needed if identified by configure
-OBJS += $(filter crypt.o getaddrinfo.o getpeereid.o inet_aton.o open.o system.o snprintf.o strerror.o strlcpy.o win32error.o win32setlocale.o, $(LIBOBJS))
+OBJS += $(filter crypt.o getaddrinfo.o getpeereid.o inet_aton.o open.o system.o snprintf.o strerror.o strlcpy.o strnlen.o win32error.o win32setlocale.o, $(LIBOBJS))
 
 ifeq ($(enable_strong_random), yes)
 OBJS += pg_strong_random.o
@@ -103,7 +103,7 @@ backend_src = $(top_srcdir)/src/backend
 # the module is needed (see filter hack in OBJS, above).
 # When you add a file here, remember to add it in the "clean" target below.
 
-chklocale.c crypt.c erand48.c getaddrinfo.c getpeereid.c inet_aton.c inet_net_ntop.c noblock.c open.c system.c pgsleep.c pg_strong_random.c pgstrcasecmp.c pqsignal.c snprintf.c strerror.c strlcpy.c thread.c win32error.c win32setlocale.c: % : $(top_srcdir)/src/port/%
+chklocale.c crypt.c erand48.c getaddrinfo.c getpeereid.c inet_aton.c inet_net_ntop.c noblock.c open.c system.c pgsleep.c pg_strong_random.c pgstrcasecmp.c pqsignal.c snprintf.c strerror.c strlcpy.c strnlen.c thread.c win32error.c win32setlocale.c: % : $(top_srcdir)/src/port/%
 	rm -f $@ && $(LN_S) $< .
 
 ip.c md5.c base64.c scram-common.c sha2.c sha2_openssl.c saslprep.c unicode_norm.c: % : $(top_srcdir)/src/common/%
@@ -155,7 +155,7 @@ clean distclean: clean-lib
 # Might be left over from a Win32 client-only build
 	rm -f pg_config_paths.h
 # Remove files we (may have) symlinked in from src/port and other places
-	rm -f chklocale.c crypt.c erand48.c getaddrinfo.c getpeereid.c inet_aton.c inet_net_ntop.c noblock.c open.c system.c pgsleep.c pg_strong_random.c pgstrcasecmp.c pqsignal.c snprintf.c strerror.c strlcpy.c thread.c win32error.c win32setlocale.c
+	rm -f chklocale.c crypt.c erand48.c getaddrinfo.c getpeereid.c inet_aton.c inet_net_ntop.c noblock.c open.c system.c pgsleep.c pg_strong_random.c pgstrcasecmp.c pqsignal.c snprintf.c strerror.c strlcpy.c strnlen.c thread.c win32error.c win32setlocale.c
 	rm -f ip.c md5.c base64.c scram-common.c sha2.c sha2_openssl.c saslprep.c unicode_norm.c
 	rm -f encnames.c wchar.c
 

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;
+}