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, 13 insertions, 5 deletions

diff --git a/src/port/unsetenv.c b/src/port/unsetenv.c
index f2028c2f834..a5f19f8db39 100644
--- a/src/port/unsetenv.c
+++ b/src/port/unsetenv.c
@@ -16,13 +16,20 @@
 #include "c.h"
 
 
-void
+int
 unsetenv(const char *name)
 {
 	char	   *envstr;
 
+	/* Error conditions, per POSIX */
+	if (name == NULL || name[0] == '\0' || strchr(name, '=') != NULL)
+	{
+		errno = EINVAL;
+		return -1;
+	}
+
 	if (getenv(name) == NULL)
-		return;					/* no work */
+		return 0;				/* no work */
 
 	/*
 	 * The technique embodied here works if libc follows the Single Unix Spec
@@ -40,11 +47,12 @@ unsetenv(const char *name)
 
 	envstr = (char *) malloc(strlen(name) + 2);
 	if (!envstr)				/* not much we can do if no memory */
-		return;
+		return -1;
 
 	/* Override the existing setting by forcibly defining the var */
 	sprintf(envstr, "%s=", name);
-	putenv(envstr);
+	if (putenv(envstr))
+		return -1;
 
 	/* Now we can clobber the variable definition this way: */
 	strcpy(envstr, "=");
@@ -53,5 +61,5 @@ unsetenv(const char *name)
 	 * This last putenv cleans up if we have multiple zero-length names as a
 	 * result of unsetting multiple things.
 	 */
-	putenv(envstr);
+	return putenv(envstr);
 }