Fix build breakage on Solaris-alikes with late-model GCC.

tglsfdc · tglsfdc · commit e6dfd068ed45 · 2025-07-23T15:44:29.000-04:00
Solaris has never bothered to add "const" to the second argument of PAM conversation procs, as all other Unixen did decades ago. This resulted in an "incompatible pointer" compiler warning when building --with-pam, but had no more serious effect than that, so we never did anything about it. However, as of GCC 14 the case is an error not warning by default. To complicate matters, recent OpenIndiana (and maybe illumos in general?) *does* supply the "const" by default, so we can't just assume that platforms using our solaris template need help. What we can do, short of building a configure-time probe, is to make solaris.h #define _PAM_LEGACY_NONCONST, which causes OpenIndiana's pam_appl.h to revert to the traditional definition, and hopefully will have no effect anywhere else. Then we can use that same symbol to control whether we include "const" in the declaration of pam_passwd_conv_proc(). Bug: #18995 Reported-by: Andrew Watkins <awatkins1966@gmail.com> Author: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/18995-82058da9ab4337a7@postgresql.org Backpatch-through: 13
diff --git a/src/backend/libpq/auth.c b/src/backend/libpq/auth.c
@@ -94,8 +94,16 @@ static int	auth_peer(hbaPort *port);
 
 #define PGSQL_PAM_SERVICE "postgresql"	/* Service name passed to PAM */
 
+/* Work around original Solaris' lack of "const" in the conv_proc signature */
+#ifdef _PAM_LEGACY_NONCONST
+#define PG_PAM_CONST
+#else
+#define PG_PAM_CONST const
+#endif
+
 static int	CheckPAMAuth(Port *port, const char *user, const char *password);
-static int	pam_passwd_conv_proc(int num_msg, const struct pam_message **msg,
+static int	pam_passwd_conv_proc(int num_msg,
+								 PG_PAM_CONST struct pam_message **msg,
 								 struct pam_response **resp, void *appdata_ptr);
 
 static struct pam_conv pam_passw_conv = {
@@ -1917,7 +1925,7 @@ auth_peer(hbaPort *port)
  */
 
 static int
-pam_passwd_conv_proc(int num_msg, const struct pam_message **msg,
+pam_passwd_conv_proc(int num_msg, PG_PAM_CONST struct pam_message **msg,
 					 struct pam_response **resp, void *appdata_ptr)
 {
 	const char *passwd;
diff --git a/src/include/port/solaris.h b/src/include/port/solaris.h
@@ -24,3 +24,12 @@
 #if defined(__i386__)
 #include <sys/isa_defs.h>
 #endif
+
+/*
+ * On original Solaris, PAM conversation procs lack a "const" in their
+ * declaration; but recent OpenIndiana versions put it there by default.
+ * The least messy way to deal with this is to define _PAM_LEGACY_NONCONST,
+ * which causes OpenIndiana to declare pam_conv per the Solaris tradition,
+ * and also use that symbol to control omitting the "const" in our own code.
+ */
+#define _PAM_LEGACY_NONCONST 1
