diff --git a/src/common/exec.c b/src/common/exec.c
index 4df16cd64bd..c207c0289fd 100644
--- a/src/common/exec.c
+++ b/src/common/exec.c
@@ -124,8 +124,10 @@ find_my_exec(const char *argv0, char *retpath)
 
 	if (!getcwd(cwd, MAXPGPATH))
 	{
+		int			save_errno = errno;
+
 		log_error(_("could not identify current directory: %s"),
-				  strerror(errno));
+				  strerror(save_errno));
 		return -1;
 	}
 
@@ -238,8 +240,10 @@ resolve_symlinks(char *path)
 	 */
 	if (!getcwd(orig_wd, MAXPGPATH))
 	{
+		int			save_errno = errno;
+
 		log_error(_("could not identify current directory: %s"),
-				  strerror(errno));
+				  strerror(save_errno));
 		return -1;
 	}
 
@@ -254,7 +258,10 @@ resolve_symlinks(char *path)
 			*lsep = '\0';
 			if (chdir(path) == -1)
 			{
-				log_error4(_("could not change directory to \"%s\": %s"), path, strerror(errno));
+				int			save_errno = errno;
+
+				log_error4(_("could not change directory to \"%s\": %s"),
+						   path, strerror(save_errno));
 				return -1;
 			}
 			fname = lsep + 1;
@@ -281,8 +288,10 @@ resolve_symlinks(char *path)
 
 	if (!getcwd(path, MAXPGPATH))
 	{
+		int			save_errno = errno;
+
 		log_error(_("could not identify current directory: %s"),
-				  strerror(errno));
+				  strerror(save_errno));
 		return -1;
 	}
 	join_path_components(path, path, link_buf);
@@ -290,7 +299,10 @@ resolve_symlinks(char *path)
 
 	if (chdir(orig_wd) == -1)
 	{
-		log_error4(_("could not change directory to \"%s\": %s"), orig_wd, strerror(errno));
+		int			save_errno = errno;
+
+		log_error4(_("could not change directory to \"%s\": %s"),
+				   orig_wd, strerror(save_errno));
 		return -1;
 	}
 #endif							/* HAVE_READLINK */
@@ -520,7 +532,10 @@ pclose_check(FILE *stream)
 	if (exitstatus == -1)
 	{
 		/* pclose() itself failed, and hopefully set errno */
-		log_error(_("pclose failed: %s"), strerror(errno));
+		int			save_errno = errno;
+
+		log_error(_("pclose failed: %s"),
+				  strerror(save_errno));
 	}
 	else
 	{
diff --git a/src/include/utils/elog.h b/src/include/utils/elog.h
index 4f4091d8cc8..6b618a52d0a 100644
--- a/src/include/utils/elog.h
+++ b/src/include/utils/elog.h
@@ -70,6 +70,23 @@
 /* SQLSTATE codes for errors are defined in a separate file */
 #include "utils/errcodes.h"
 
+/*
+ * Provide a way to prevent "errno" from being accidentally used inside an
+ * elog() or ereport() invocation.  Since we know that some operating systems
+ * define errno as something involving a function call, we'll put a local
+ * variable of the same name as that function in the local scope to force a
+ * compile error.  On platforms that don't define errno in that way, nothing
+ * happens, so we get no warning ... but we can live with that as long as it
+ * happens on some popular platforms.
+ */
+#if defined(errno) && defined(__linux__)
+#define pg_prevent_errno_in_scope() int __errno_location pg_attribute_unused()
+#elif defined(errno) && (defined(__darwin__) || defined(__freebsd__))
+#define pg_prevent_errno_in_scope() int __error pg_attribute_unused()
+#else
+#define pg_prevent_errno_in_scope()
+#endif
+
 
 /*----------
  * New-style error reporting API: to be used in this way:
@@ -103,6 +120,7 @@
 #ifdef HAVE__BUILTIN_CONSTANT_P
 #define ereport_domain(elevel, domain, rest)	\
 	do { \
+		pg_prevent_errno_in_scope(); \
 		if (errstart(elevel, __FILE__, __LINE__, PG_FUNCNAME_MACRO, domain)) \
 			errfinish rest; \
 		if (__builtin_constant_p(elevel) && (elevel) >= ERROR) \
@@ -112,6 +130,7 @@
 #define ereport_domain(elevel, domain, rest)	\
 	do { \
 		const int elevel_ = (elevel); \
+		pg_prevent_errno_in_scope(); \
 		if (errstart(elevel_, __FILE__, __LINE__, PG_FUNCNAME_MACRO, domain)) \
 			errfinish rest; \
 		if (elevel_ >= ERROR) \
@@ -198,6 +217,7 @@ extern int	getinternalerrposition(void);
 #ifdef HAVE__BUILTIN_CONSTANT_P
 #define elog(elevel, ...)  \
 	do { \
+		pg_prevent_errno_in_scope(); \
 		elog_start(__FILE__, __LINE__, PG_FUNCNAME_MACRO); \
 		elog_finish(elevel, __VA_ARGS__); \
 		if (__builtin_constant_p(elevel) && (elevel) >= ERROR) \
@@ -206,6 +226,7 @@ extern int	getinternalerrposition(void);
 #else							/* !HAVE__BUILTIN_CONSTANT_P */
 #define elog(elevel, ...)  \
 	do { \
+		pg_prevent_errno_in_scope(); \
 		elog_start(__FILE__, __LINE__, PG_FUNCNAME_MACRO); \
 		{ \
 			const int elevel_ = (elevel); \