Keep pg_config overrides in separate pg_config_overrides.h file

We've previously managed these in the Makefile inline, but that is
very hard to read, and not necessary, since we can simply concatenate
the override file to pg_config.h during the source extraction process.

Makefile

@@ -127,54 +127,11 @@ $(PGDIR):
 	cd $(PGDIR); make -C src/port pg_config_paths.h
 	cd $(PGDIR); make -C src/backend generated-headers
 	cd $(PGDIR); make -C src/backend parser-recursive # Triggers copying of includes to where they belong, as well as generating gram.c/scan.c
-	# This causes compatibility problems on some Linux distros, with "xlocale.h" not being available
-	echo "#undef HAVE_LOCALE_T" >> $(PGDIR)/src/include/pg_config.h
-	echo "#undef LOCALE_T_IN_XLOCALE" >> $(PGDIR)/src/include/pg_config.h
-	echo "#undef WCSTOMBS_L_IN_XLOCALE" >> $(PGDIR)/src/include/pg_config.h
-	# Support 32-bit systems without reconfiguring
-	echo "#undef PG_INT128_TYPE" >> $(PGDIR)/src/include/pg_config.h
-	# Support gcc earlier than 4.6.0 without reconfiguring
-	echo "#undef HAVE__STATIC_ASSERT" >> $(PGDIR)/src/include/pg_config.h
 	# Avoid problems with static asserts
 	echo "#undef StaticAssertDecl" >> $(PGDIR)/src/include/c.h
 	echo "#define StaticAssertDecl(condition, errmessage)" >> $(PGDIR)/src/include/c.h
-	# Avoid dependency on execinfo (requires extra library on musl-libc based systems)
-	echo "#undef HAVE_EXECINFO_H" >> $(PGDIR)/src/include/pg_config.h
-	echo "#undef HAVE_BACKTRACE_SYMBOLS" >> $(PGDIR)/src/include/pg_config.h
-	# Avoid dependency on hardware popcount instructions (POPQNTQ) on x86
-	echo "#undef HAVE_X86_64_POPCNTQ" >> $(PGDIR)/src/include/pg_config.h
-	# Avoid dependency on cpuid.h (only supported on x86 systems)
-	echo "#undef HAVE__GET_CPUID" >> $(PGDIR)/src/include/pg_config.h
-	# Avoid CRC extension usage to ensure we are not architecture-dependent
-	echo "#undef USE_ARMV8_CRC32C" >> $(PGDIR)/src/include/pg_config.h
-	echo "#undef USE_SSE42_CRC32C_WITH_RUNTIME_CHECK" >> $(PGDIR)/src/include/pg_config.h
-	# Ensure we don't fail on systems that have strchrnul support (FreeBSD and NetBSD)
-	echo "#include <stdlib.h>" >>  $(PGDIR)/src/include/pg_config.h
-	echo "#if defined(__FreeBSD__) || defined(__NetBSD__) || (defined(__GLIBC__) && ((__GLIBC__ == 2 && __GLIBC_MINOR__ >= 38) || __GLIBC__ > 2))" >> $(PGDIR)/src/include/pg_config.h
-	echo "#define HAVE_STRCHRNUL" >> $(PGDIR)/src/include/pg_config.h
-	echo "#endif" >> $(PGDIR)/src/include/pg_config.h
-	# Optionally support 32-bit
-	echo "#if defined(_WIN32) || __SIZEOF_POINTER__ == 4" >> $(PGDIR)/src/include/pg_config.h
-	echo "#undef ALIGNOF_DOUBLE" >> $(PGDIR)/src/include/pg_config.h
-	echo "#define ALIGNOF_DOUBLE 4" >> $(PGDIR)/src/include/pg_config.h
-	echo "#undef ALIGNOF_LONG" >> $(PGDIR)/src/include/pg_config.h
-	echo "#define ALIGNOF_LONG 4" >> $(PGDIR)/src/include/pg_config.h
-	echo "#define ALIGNOF_LONG_LONG_INT 4" >> $(PGDIR)/src/include/pg_config.h
-	echo "#undef ALIGNOF_PG_INT128_TYPE" >> $(PGDIR)/src/include/pg_config.h
-	echo "#undef HAVE_LONG_INT_64" >> $(PGDIR)/src/include/pg_config.h
-	echo "#define HAVE_LONG_LONG_INT_64 1" >> $(PGDIR)/src/include/pg_config.h
-	echo "#undef INT64_MODIFIER" >> $(PGDIR)/src/include/pg_config.h
-	echo "#define INT64_MODIFIER \"ll\"" >> $(PGDIR)/src/include/pg_config.h
-	echo "#undef PG_INT128_TYPE" >> $(PGDIR)/src/include/pg_config.h
-	echo "#undef PG_INT64_TYPE" >> $(PGDIR)/src/include/pg_config.h
-	echo "#define PG_INT64_TYPE long long int" >> $(PGDIR)/src/include/pg_config.h
-	echo "#undef SIZEOF_LONG" >> $(PGDIR)/src/include/pg_config.h
-	echo "#define SIZEOF_LONG 4" >> $(PGDIR)/src/include/pg_config.h
-	echo "#undef SIZEOF_SIZE_T" >> $(PGDIR)/src/include/pg_config.h
-	echo "#define SIZEOF_SIZE_T 4" >> $(PGDIR)/src/include/pg_config.h
-	echo "#undef SIZEOF_VOID_P" >> $(PGDIR)/src/include/pg_config.h
-	echo "#define SIZEOF_VOID_P 4" >> $(PGDIR)/src/include/pg_config.h
-	echo "#endif" >> $(PGDIR)/src/include/pg_config.h
+	# Add pg_config.h overrides
+	cat scripts/pg_config_overrides.h >> $(PGDIR)/src/include/pg_config.h
 
 extract_source: $(PGDIR)
 	-@ $(RM) -rf ./src/postgres/

scripts/pg_config_overrides.h

@@ -0,0 +1,52 @@
+/* This causes compatibility problems on some Linux distros, with "xlocale.h" not being available */
+#undef HAVE_LOCALE_T
+#undef LOCALE_T_IN_XLOCALE
+#undef WCSTOMBS_L_IN_XLOCALE
+
+/* Support gcc earlier than 4.6.0 and MSVC */
+#undef HAVE__STATIC_ASSERT
+
+/* Avoid dependency on execinfo (requires extra library on musl-libc based systems, not supported on Windows) */
+#undef HAVE_EXECINFO_H
+#undef HAVE_BACKTRACE_SYMBOLS
+
+/* Avoid dependency on hardware popcount instructions (POPQNTQ) on x86 */
+#undef HAVE_X86_64_POPCNTQ
+
+/* Avoid dependency on cpuid.h (only supported on x86 systems) */
+#undef HAVE__GET_CPUID
+
+/* Avoid CRC extension usage to ensure we are not architecture-dependent */
+#undef USE_ARMV8_CRC32C
+#undef USE_SSE42_CRC32C_WITH_RUNTIME_CHECK
+
+/* Ensure we do not fail on systems that have strchrnul support (FreeBSD, NetBSD and newer glibc) */
+#include <stdlib.h>
+#if defined(__FreeBSD__) || defined(__NetBSD__) || (defined(__GLIBC__) && ((__GLIBC__ == 2 && __GLIBC_MINOR__ >= 38) || __GLIBC__ > 2))
+#define HAVE_STRCHRNUL
+#endif
+
+/* 32-bit */
+#if defined(_WIN32) || __SIZEOF_POINTER__ == 4
+#undef ALIGNOF_DOUBLE
+#define ALIGNOF_DOUBLE 4
+#undef ALIGNOF_LONG
+#define ALIGNOF_LONG 4
+#define ALIGNOF_LONG_LONG_INT 4
+#undef ALIGNOF_PG_INT128_TYPE
+#undef HAVE_LONG_INT_64
+#define HAVE_LONG_LONG_INT_64 1
+#undef INT64_MODIFIER
+#define INT64_MODIFIER "ll"
+#undef PG_INT128_TYPE
+#undef PG_INT64_TYPE
+#define PG_INT64_TYPE long long int
+#undef SIZEOF_LONG
+#define SIZEOF_LONG 4
+#undef SIZEOF_OFF_T
+#define SIZEOF_OFF_T 4
+#undef SIZEOF_SIZE_T
+#define SIZEOF_SIZE_T 4
+#undef SIZEOF_VOID_P
+#define SIZEOF_VOID_P 4
+#endif

src/postgres/include/pg_config.h

@@ -826,21 +826,35 @@
 
 /* Define to how the compiler spells `typeof'. */
 /* #undef typeof */
+/* This causes compatibility problems on some Linux distros, with "xlocale.h" not being available */
 #undef HAVE_LOCALE_T
 #undef LOCALE_T_IN_XLOCALE
 #undef WCSTOMBS_L_IN_XLOCALE
-#undef PG_INT128_TYPE
+
+/* Support gcc earlier than 4.6.0 and MSVC */
 #undef HAVE__STATIC_ASSERT
+
+/* Avoid dependency on execinfo (requires extra library on musl-libc based systems, not supported on Windows) */
 #undef HAVE_EXECINFO_H
 #undef HAVE_BACKTRACE_SYMBOLS
+
+/* Avoid dependency on hardware popcount instructions (POPQNTQ) on x86 */
 #undef HAVE_X86_64_POPCNTQ
+
+/* Avoid dependency on cpuid.h (only supported on x86 systems) */
 #undef HAVE__GET_CPUID
+
+/* Avoid CRC extension usage to ensure we are not architecture-dependent */
 #undef USE_ARMV8_CRC32C
 #undef USE_SSE42_CRC32C_WITH_RUNTIME_CHECK
+
+/* Ensure we do not fail on systems that have strchrnul support (FreeBSD, NetBSD and newer glibc) */
 #include <stdlib.h>
 #if defined(__FreeBSD__) || defined(__NetBSD__) || (defined(__GLIBC__) && ((__GLIBC__ == 2 && __GLIBC_MINOR__ >= 38) || __GLIBC__ > 2))
 #define HAVE_STRCHRNUL
 #endif
+
+/* 32-bit */
 #if defined(_WIN32) || __SIZEOF_POINTER__ == 4
 #undef ALIGNOF_DOUBLE
 #define ALIGNOF_DOUBLE 4
@@ -857,6 +871,8 @@
 #define PG_INT64_TYPE long long int
 #undef SIZEOF_LONG
 #define SIZEOF_LONG 4
+#undef SIZEOF_OFF_T
+#define SIZEOF_OFF_T 4
 #undef SIZEOF_SIZE_T
 #define SIZEOF_SIZE_T 4
 #undef SIZEOF_VOID_P