Use setenv() in preference to putenv().

Since at least 2001 we've used putenv() and avoided setenv(), on the
grounds that the latter was unportable and not in POSIX.  However,
POSIX added it that same year, and by now the situation has reversed:
setenv() is probably more portable than putenv(), since POSIX now
treats the latter as not being a core function.  And setenv() has
cleaner semantics too.  So, let's reverse that old policy.

This commit adds a simple src/port/ implementation of setenv() for
any stragglers (we have one in the buildfarm, but I'd not be surprised
if that code is never used in the field).  More importantly, extend
win32env.c to also support setenv().  Then, replace usages of putenv()
with setenv(), and get rid of some ad-hoc implementations of setenv()
wannabees.

Also, adjust our src/port/ implementation of unsetenv() to follow the
POSIX spec that it returns an error indicator, rather than returning
void as per the ancient BSD convention.  I don't feel a need to make
all the call sites check for errors, but the portability stub ought
to match real-world practice.

Discussion: https://postgr.es/m/2065122.1609212051@sss.pgh.pa.us

1 files changed, 3 insertions, 19 deletions

diff --git a/src/common/exec.c b/src/common/exec.c
index 78bb486f999..773afd080c0 100644
--- a/src/common/exec.c
+++ b/src/common/exec.c
@@ -435,9 +435,6 @@ set_pglocale_pgservice(const char *argv0, const char *app)
 {
 	char		path[MAXPGPATH];
 	char		my_exec_path[MAXPGPATH];
-	char		env_path[MAXPGPATH + sizeof("PGSYSCONFDIR=")];	/* longer than
-																 * PGLOCALEDIR */
-	char	   *dup_path;
 
 	/* don't set LC_ALL in the backend */
 	if (strcmp(app, PG_TEXTDOMAIN("postgres")) != 0)
@@ -462,28 +459,15 @@ set_pglocale_pgservice(const char *argv0, const char *app)
 	get_locale_path(my_exec_path, path);
 	bindtextdomain(app, path);
 	textdomain(app);
-
-	if (getenv("PGLOCALEDIR") == NULL)
-	{
-		/* set for libpq to use */
-		snprintf(env_path, sizeof(env_path), "PGLOCALEDIR=%s", path);
-		canonicalize_path(env_path + 12);
-		dup_path = strdup(env_path);
-		if (dup_path)
-			putenv(dup_path);
-	}
+	/* set for libpq to use, but don't override existing setting */
+	setenv("PGLOCALEDIR", path, 0);
 #endif
 
 	if (getenv("PGSYSCONFDIR") == NULL)
 	{
 		get_etc_path(my_exec_path, path);
-
 		/* set for libpq to use */
-		snprintf(env_path, sizeof(env_path), "PGSYSCONFDIR=%s", path);
-		canonicalize_path(env_path + 13);
-		dup_path = strdup(env_path);
-		if (dup_path)
-			putenv(dup_path);
+		setenv("PGSYSCONFDIR", path, 0);
 	}
 }