[Peter Eisentraut <peter.eisentraut@2ndquadrant.com>]

I noticed that when you want to define EXEC_BACKEND, perhaps to do some 
non-Windows testing of that option, it's not clear how to do that.  I 
would have expected it in pg_config_manual.h, but it's actually in 
configure.in and in MSBuildProject.pm.  So if you want to define it 
yourself, you kind of have to make up your own way to do it.

I don't see why this should be like that.  I propose the attached patch 
to move the thing to pg_config_manual.h.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

Attachments:

0001-Define-EXEC_BACKEND-in-pg_config_manual.h.patch (text/plain, 3.6K) download
From c7d574d3b9f363cc44daf45c543ab4addfa25afd Mon Sep 17 00:00:00 2001
From: Peter Eisentraut <peter@eisentraut.org>
Date: Thu, 19 Mar 2020 16:32:02 +0100
Subject: [PATCH] Define EXEC_BACKEND in pg_config_manual.h

It was for unclear reasons defined in a separate location, which makes
it more cumbersome to override for testing, and it also did not have
any prominent documentation.  Move to pg_config_manual.h, where
similar things are already collected.
---
 configure                        |  2 +-
 configure.in                     |  2 +-
 src/include/pg_config_manual.h   | 13 +++++++++++++
 src/tools/msvc/MSBuildProject.pm |  2 +-
 4 files changed, 16 insertions(+), 3 deletions(-)

diff --git a/configure b/configure
index a7cf71b3f1..899116517c 100755
--- a/configure
+++ b/configure
@@ -6906,7 +6906,7 @@ fi
 
 # We already have this in Makefile.win32, but configure needs it too
 if test "$PORTNAME" = "win32"; then
-  CPPFLAGS="$CPPFLAGS -I$srcdir/src/include/port/win32 -DEXEC_BACKEND"
+  CPPFLAGS="$CPPFLAGS -I$srcdir/src/include/port/win32"
 fi
 
 # Now that we're done automatically adding stuff to C[XX]FLAGS, put back the
diff --git a/configure.in b/configure.in
index d36a7e94b3..ecdf172396 100644
--- a/configure.in
+++ b/configure.in
@@ -600,7 +600,7 @@ fi
 
 # We already have this in Makefile.win32, but configure needs it too
 if test "$PORTNAME" = "win32"; then
-  CPPFLAGS="$CPPFLAGS -I$srcdir/src/include/port/win32 -DEXEC_BACKEND"
+  CPPFLAGS="$CPPFLAGS -I$srcdir/src/include/port/win32"
 fi
 
 # Now that we're done automatically adding stuff to C[XX]FLAGS, put back the
diff --git a/src/include/pg_config_manual.h b/src/include/pg_config_manual.h
index d74a8dd808..b7410ff51e 100644
--- a/src/include/pg_config_manual.h
+++ b/src/include/pg_config_manual.h
@@ -122,6 +122,19 @@
  */
 #define ALIGNOF_BUFFER	32
 
+/*
+ * If EXEC_BACKEND is defined, the postmaster uses an alternative method for
+ * starting subprocesses: Instead of simply using fork(), as is standard on
+ * Unix platforms, it uses fork()+exec() or something equivalent on Windows,
+ * as well as lots of extra code to bring the required global state to those
+ * new processes.  This must be enabled on Windows (because there is no
+ * fork()).  On other platforms, it's only useful for verifying those
+ * otherwise Windows-specific code paths.
+ */
+#if defined(WIN32) && !defined(__CYGWIN__)
+#define EXEC_BACKEND
+#endif
+
 /*
  * Disable UNIX sockets for certain operating systems.
  */
diff --git a/src/tools/msvc/MSBuildProject.pm b/src/tools/msvc/MSBuildProject.pm
index 823357c023..ebb169e201 100644
--- a/src/tools/msvc/MSBuildProject.pm
+++ b/src/tools/msvc/MSBuildProject.pm
@@ -320,7 +320,7 @@ sub WriteItemDefinitionGroup
     <ClCompile>
       <Optimization>$p->{opt}</Optimization>
       <AdditionalIncludeDirectories>$self->{prefixincludes}src/include;src/include/port/win32;src/include/port/win32_msvc;$includes\%(AdditionalIncludeDirectories)</AdditionalIncludeDirectories>
-      <PreprocessorDefinitions>WIN32;_WINDOWS;__WINDOWS__;__WIN32__;EXEC_BACKEND;WIN32_STACK_RLIMIT=4194304;_CRT_SECURE_NO_DEPRECATE;_CRT_NONSTDC_NO_DEPRECATE$self->{defines}$p->{defs}\%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>WIN32;_WINDOWS;__WINDOWS__;__WIN32__;WIN32_STACK_RLIMIT=4194304;_CRT_SECURE_NO_DEPRECATE;_CRT_NONSTDC_NO_DEPRECATE$self->{defines}$p->{defs}\%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <StringPooling>$p->{strpool}</StringPooling>
       <RuntimeLibrary>$p->{runtime}</RuntimeLibrary>
       <DisableSpecificWarnings>$self->{disablewarnings};\%(DisableSpecificWarnings)</DisableSpecificWarnings>
-- 
2.25.0