Second try at a portable unsetenv().

configure

@@ -11744,7 +11744,8 @@ fi
 
 
 
-for ac_func in crypt fseeko getopt getrusage inet_aton random rint srandom strcasecmp strdup strerror strtol strtoul
+
+for ac_func in crypt fseeko getopt getrusage inet_aton random rint srandom strcasecmp strdup strerror strtol strtoul unsetenv
 do
 as_ac_var=`echo "ac_cv_func_$ac_func" | $as_tr_sh`
 echo "$as_me:$LINENO: checking for $ac_func" >&5

configure.in

 dnl Process this file with autoconf to produce a configure script.
-dnl $PostgreSQL: pgsql/configure.in,v 1.343 2004/04/30 16:08:01 momjian Exp $
+dnl $PostgreSQL: pgsql/configure.in,v 1.344 2004/05/05 21:18:29 tgl Exp $
 dnl
 dnl Developers, please strive to achieve this order:
 dnl
@@ -858,7 +858,7 @@ else
   AC_CHECK_FUNCS([fpclass fp_class fp_class_d class], [break])
 fi
 
-AC_REPLACE_FUNCS([crypt fseeko getopt getrusage inet_aton random rint srandom strcasecmp strdup strerror strtol strtoul])
+AC_REPLACE_FUNCS([crypt fseeko getopt getrusage inet_aton random rint srandom strcasecmp strdup strerror strtol strtoul unsetenv])
 
 # system's version of getaddrinfo(), if any, may be used only if we found
 # a definition for struct addrinfo; see notes in src/include/getaddrinfo.h

src/bin/initdb/initdb.c

@@ -43,7 +43,7 @@
  * Portions Copyright (c) 1994, Regents of the University of California
  * Portions taken from FreeBSD.
  *
- * $PostgreSQL: pgsql/src/bin/initdb/initdb.c,v 1.24 2004/05/05 16:09:31 tgl Exp $
+ * $PostgreSQL: pgsql/src/bin/initdb/initdb.c,v 1.25 2004/05/05 21:18:29 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -263,24 +263,6 @@ xstrdup(const char *s)
 	return result;
 }
 
-/*
- * unsetenv() doesn't exist everywhere, so emulate it with this ugly
- * but well-tested technique (borrowed from backend's variable.c).
- */
-static void
-pg_unsetenv(const char *varname)
-{
-	char  *envstr = xmalloc(strlen(varname) + 2);
-
-	/* First, override any existing setting by forcibly defining the var */
-	sprintf(envstr, "%s=", varname);
-	putenv(envstr);
-
-	/* Now we can clobber the variable definition this way: */
-	strcpy(envstr, "=");
-	putenv(envstr);
-}
-
 /*
  * delete a directory tree recursively
  * assumes path points to a valid directory
@@ -1260,10 +1242,10 @@ bootstrap_template1(char *short_version)
 	snprintf(cmd, sizeof(cmd), "LC_CTYPE=%s", lc_ctype);
 	putenv(xstrdup(cmd));
 
-	pg_unsetenv("LC_ALL");
+	unsetenv("LC_ALL");
 
 	/* Also ensure backend isn't confused by this environment var: */
-	pg_unsetenv("PGCLIENTENCODING");
+	unsetenv("PGCLIENTENCODING");
 
 	snprintf(cmd, sizeof(cmd),
 			 "\"%s/postgres\" -boot -x1 %s %s template1",

src/include/c.h

@@ -12,7 +12,7 @@
  * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
  * Portions Copyright (c) 1994, Regents of the University of California
  *
- * $PostgreSQL: pgsql/src/include/c.h,v 1.162 2004/04/30 20:47:33 momjian Exp $
+ * $PostgreSQL: pgsql/src/include/c.h,v 1.163 2004/05/05 21:18:29 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -720,6 +720,10 @@ extern int	vsnprintf(char *str, size_t count, const char *fmt, va_list args);
 #define memmove(d, s, c)		bcopy(s, d, c)
 #endif
 
+#ifndef HAVE_UNSETENV
+extern void unsetenv(const char *name);
+#endif
+
 #ifndef DLLIMPORT
 #define DLLIMPORT				/* no special DLL markers on most ports */
 #endif

src/include/pg_config.h.in

@@ -530,6 +530,9 @@
 /* Define to 1 if you have unix sockets. */
 #undef HAVE_UNIX_SOCKETS
 
+/* Define to 1 if you have the `unsetenv' function. */
+#undef HAVE_UNSETENV
+
 /* Define to 1 if you have the `utime' function. */
 #undef HAVE_UTIME
 

src/port/unsetenv.c

+/*-------------------------------------------------------------------------
+ *
+ * unsetenv.c
+ *	  unsetenv() emulation for machines without it
+ *
+ * Portions Copyright (c) 1996-2003, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *	  $PostgreSQL: pgsql/src/port/unsetenv.c,v 1.1 2004/05/05 21:18:29 tgl Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
+
+#include "c.h"
+
+
+void
+unsetenv(const char *name)
+{
+	char  *envstr;
+
+	if (getenv(name) == NULL)
+		return;					/* no work */
+
+	/*
+	 * The technique embodied here works if libc follows the Single Unix Spec
+	 * and actually uses the storage passed to putenv() to hold the environ
+	 * entry.  When we clobber the entry in the second step we are ensuring
+	 * that we zap the actual environ member.  However, there are some libc
+	 * implementations (notably recent BSDs) that do not obey SUS but copy
+	 * the presented string.  This method fails on such platforms.  Hopefully
+	 * all such platforms have unsetenv() and thus won't be using this hack.
+	 *
+	 * Note that repeatedly setting and unsetting a var using this code
+	 * will leak memory.
+	 */
+
+	envstr = (char *) malloc(strlen(name) + 2);
+	if (!envstr)				/* not much we can do if no memory */
+		return;
+
+	/* Override the existing setting by forcibly defining the var */
+	sprintf(envstr, "%s=", name);
+	putenv(envstr);
+
+	/* Now we can clobber the variable definition this way: */
+	strcpy(envstr, "=");
+
+	/*
+	 * This last putenv cleans up if we have multiple zero-length names
+	 * as a result of unsetting multiple things.
+	 */
+	putenv(envstr);
+}