10 files changed, 55 insertions, 21 deletions
diff --git a/configure b/configure
index d6ce3945256..629fe8ecf03 100755
--- a/configure
+++ b/configure
@@ -14786,6 +14786,12 @@ _ACEOF
 
 
 
+if test "$ac_cv_header_stdbool_h" = yes -a "$ac_cv_sizeof_bool" = 1; then
+
+$as_echo "#define PG_USE_STDBOOL 1" >>confdefs.h
+
+fi
+
 
 ##
 ## Functions, global variables
diff --git a/configure.in b/configure.in
index 5bd31a876e8..1ea1c465504 100644
--- a/configure.in
+++ b/configure.in
@@ -1593,6 +1593,13 @@ AC_CHECK_SIZEOF([bool], [],
 #include <stdbool.h>
 #endif])
 
+dnl We use <stdbool.h> if we have it and it declares type bool as having
+dnl size 1.  Otherwise, c.h will fall back to declaring bool as unsigned char.
+if test "$ac_cv_header_stdbool_h" = yes -a "$ac_cv_sizeof_bool" = 1; then
+  AC_DEFINE([PG_USE_STDBOOL], 1,
+            [Define to 1 to use <stdbool.h> to define type bool.])
+fi
+
 
 ##
 ## Functions, global variables
diff --git a/src/backend/utils/fmgr/dfmgr.c b/src/backend/utils/fmgr/dfmgr.c
index be684786d64..c8d2cef35ff 100644
--- a/src/backend/utils/fmgr/dfmgr.c
+++ b/src/backend/utils/fmgr/dfmgr.c
@@ -23,7 +23,7 @@
  * On macOS, <dlfcn.h> insists on including <stdbool.h>.  If we're not
  * using stdbool, undef bool to undo the damage.
  */
-#ifndef USE_STDBOOL
+#ifndef PG_USE_STDBOOL
 #ifdef bool
 #undef bool
 #endif
diff --git a/src/include/c.h b/src/include/c.h
index c95acd35f7f..802a731267f 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -288,20 +288,21 @@
  * bool
  *		Boolean value, either true or false.
  *
- * Use stdbool.h if available and its bool has size 1.  That's useful for
+ * We use stdbool.h if available and its bool has size 1.  That's useful for
  * better compiler and debugger output and for compatibility with third-party
  * libraries.  But PostgreSQL currently cannot deal with bool of other sizes;
  * there are static assertions around the code to prevent that.
  *
  * For C++ compilers, we assume the compiler has a compatible built-in
  * definition of bool.
+ *
+ * See also the version of this code in src/interfaces/ecpg/include/ecpglib.h.
  */
 
 #ifndef __cplusplus
 
-#if defined(HAVE_STDBOOL_H) && SIZEOF_BOOL == 1
+#ifdef PG_USE_STDBOOL
 #include <stdbool.h>
-#define USE_STDBOOL 1
 #else
 
 #ifndef bool
@@ -316,7 +317,7 @@ typedef unsigned char bool;
 #define false	((bool) 0)
 #endif
 
-#endif
+#endif							/* not PG_USE_STDBOOL */
 #endif							/* not C++ */
 
 
diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in
index 25a48d3ba78..fc22526b7e3 100644
--- a/src/include/pg_config.h.in
+++ b/src/include/pg_config.h.in
@@ -829,6 +829,9 @@
 /* Define to best printf format archetype, usually gnu_printf if available. */
 #undef PG_PRINTF_ATTRIBUTE
 
+/* Define to 1 to use <stdbool.h> to define type bool. */
+#undef PG_USE_STDBOOL
+
 /* PostgreSQL version as a string */
 #undef PG_VERSION
 
diff --git a/src/include/pg_config.h.win32 b/src/include/pg_config.h.win32
index 6b67fb06308..6c98ef49162 100644
--- a/src/include/pg_config.h.win32
+++ b/src/include/pg_config.h.win32
@@ -624,6 +624,9 @@
    (--with-krb-srvnam=NAME) */
 #define PG_KRB_SRVNAM "postgres"
 
+/* Define to 1 to use <stdbool.h> to define type bool. */
+#define PG_USE_STDBOOL 1
+
 /* A string containing the version number, platform, and C compiler */
 #define PG_VERSION_STR "Uninitialized version string (win32)"
 
diff --git a/src/interfaces/ecpg/include/ecpg_config.h.in b/src/interfaces/ecpg/include/ecpg_config.h.in
index c18556130ef..17e93c40dbb 100644
--- a/src/interfaces/ecpg/include/ecpg_config.h.in
+++ b/src/interfaces/ecpg/include/ecpg_config.h.in
@@ -10,6 +10,9 @@
 /* Define to 1 if `long long int' works and is 64 bits. */
 #undef HAVE_LONG_LONG_INT_64
 
+/* Define to 1 to use <stdbool.h> to define type bool. */
+#undef PG_USE_STDBOOL
+
 /* Define to 1 to build client libraries as thread-safe code.
  *    (--enable-thread-safety) */
 #undef ENABLE_THREAD_SAFETY
diff --git a/src/interfaces/ecpg/include/ecpglib.h b/src/interfaces/ecpg/include/ecpglib.h
index de9c76aefc3..c65073f15ac 100644
--- a/src/interfaces/ecpg/include/ecpglib.h
+++ b/src/interfaces/ecpg/include/ecpglib.h
@@ -1,6 +1,6 @@
 /*
- * this is a small part of c.h since we don't want to leak all postgres
- * definitions into ecpg programs
+ * Client-visible declarations for ecpglib
+ *
  * src/interfaces/ecpg/include/ecpglib.h
  */
 
@@ -8,30 +8,40 @@
 #define _ECPGLIB_H
 
 #include "libpq-fe.h"
+#include "ecpg_config.h"
 #include "ecpgtype.h"
 #include "sqlca.h"
 #include <string.h>
 
+/*
+ * This is a small extract from c.h since we don't want to leak all postgres
+ * definitions into ecpg programs; but we need to know what bool is.
+ */
 #ifndef __cplusplus
-#ifndef bool
-#define bool char
-#endif							/* ndef bool */
+
+#ifdef PG_USE_STDBOOL
+#include <stdbool.h>
+#else
+
+/*
+ * We assume bool has been defined if true and false are.  This avoids
+ * duplicate-typedef errors if this file is included after c.h.
+ */
+#if !(defined(true) && defined(false))
+typedef unsigned char bool;
+#endif
 
 #ifndef true
 #define true	((bool) 1)
-#endif							/* ndef true */
+#endif
+
 #ifndef false
 #define false	((bool) 0)
-#endif							/* ndef false */
-#endif							/* not C++ */
+#endif
 
-#ifndef TRUE
-#define TRUE	1
-#endif							/* TRUE */
+#endif							/* not PG_USE_STDBOOL */
+#endif							/* not C++ */
 
-#ifndef FALSE
-#define FALSE	0
-#endif							/* FALSE */
 
 #ifdef __cplusplus
 extern "C"
diff --git a/src/pl/plperl/plperl.h b/src/pl/plperl/plperl.h
index 3748158a86d..7ae3c69c086 100644
--- a/src/pl/plperl/plperl.h
+++ b/src/pl/plperl/plperl.h
@@ -64,7 +64,7 @@
  * warnings.  If PostgreSQL does not but Perl does, we need to undefine bool
  * after we include the Perl headers; see below.
  */
-#ifdef USE_STDBOOL
+#ifdef PG_USE_STDBOOL
 #define HAS_BOOL 1
 #endif
 
@@ -175,7 +175,7 @@
  * makes bool a macro, but our own replacement is a typedef, so the undef
  * makes ours visible again).
  */
-#ifndef USE_STDBOOL
+#ifndef PG_USE_STDBOOL
 #ifdef bool
 #undef bool
 #endif
diff --git a/src/tools/msvc/Solution.pm b/src/tools/msvc/Solution.pm
index a6958273ac1..7f179f194be 100644
--- a/src/tools/msvc/Solution.pm
+++ b/src/tools/msvc/Solution.pm
@@ -513,6 +513,7 @@ sub GenerateFiles
 		print $o <<EOF;
 #define HAVE_LONG_LONG_INT 1
 #define HAVE_LONG_LONG_INT_64 1
+#define PG_USE_STDBOOL 1
 #define ENABLE_THREAD_SAFETY 1
 EOF
 		close($o);