Re: PG vs macOS Mojave

So it seems like there are two ways we could go about this.  One is
to go back to the scheme of adding an -isysroot switch to CPPFLAGS,
where it'd have global effects.  We could make this slightly less
painful for scenarios like Jakob's if we set things up in Makefile.global
this way:

CPPFLAGS = -isysroot $(PG_SYSROOT)
PG_SYSROOT = /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk

and then, if you need to build on a different SDK version without
reconfiguring, you can do something like "make PG_SYSROOT=/proper/path".
I coded this up, as attached, and it seems to work but it's still not all
that friendly for such cases.

The other idea that's occurred to me is to go back to the scheme of
commit 68fc227dd, where we inject the sysroot path into just the -I
switches used for PL/Perl and PL/Tcl.  We could improve on that
commit by injecting it symbolically similar to what I did here, ie
what ends up in the configure output is

PG_SYSROOT = /Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.14.sdk

perl_includespec = -I $(PG_SYSROOT)/System/Library/Perl/5.18/darwin-thread-multi-2level/CORE

Then somebody who wants to build on a different SDK version still needs
to do "make PG_SYSROOT=/proper/path", but only if they're trying to
build PL/Perl or related extensions.  So this second way seems uglier
in some sense but less likely to cause problems for most people.

Either way I guess we'd need to document it rather than just hoping
it's invisible.

Thoughts?

            regards, tom lane

diff --git a/configure b/configure
index 43ae8c8..0686941 100755
*** a/configure
--- b/configure
*************** ac_includes_default="\
*** 627,632 ****
--- 627,633 ----

  ac_subst_vars='LTLIBOBJS
  vpath_build
+ PG_SYSROOT
  PG_VERSION_NUM
  PROVE
  FOP
*************** _ACEOF
*** 18815,18820 ****
--- 18816,18830 ----



+ # If we are inserting PG_SYSROOT into CPPFLAGS, do so symbolically not
+ # literally, so that it's possible to override it at build time using
+ # a command like "make ... PG_SYSROOT=path".  This has to be done after
+ # we've finished all configure checks that depend on CPPFLAGS.
+ if test x"$PG_SYSROOT" != x; then
+   CPPFLAGS=`echo "$CPPFLAGS" | sed -e "s| $PG_SYSROOT | \\\$(PG_SYSROOT) |"`
+ fi
+
+

  # Begin output steps

diff --git a/configure.in b/configure.in
index 519ecd5..7586deb 100644
*** a/configure.in
--- b/configure.in
*************** $AWK '{printf "%d%04d", $1, $2}'`"]
*** 2357,2362 ****
--- 2357,2371 ----
  AC_DEFINE_UNQUOTED(PG_VERSION_NUM, $PG_VERSION_NUM, [PostgreSQL version as a number])
  AC_SUBST(PG_VERSION_NUM)

+ # If we are inserting PG_SYSROOT into CPPFLAGS, do so symbolically not
+ # literally, so that it's possible to override it at build time using
+ # a command like "make ... PG_SYSROOT=path".  This has to be done after
+ # we've finished all configure checks that depend on CPPFLAGS.
+ if test x"$PG_SYSROOT" != x; then
+   CPPFLAGS=`echo "$CPPFLAGS" | sed -e "s| $PG_SYSROOT | \\\$(PG_SYSROOT) |"`
+ fi
+ AC_SUBST(PG_SYSROOT)
+

  # Begin output steps

diff --git a/src/Makefile.global.in b/src/Makefile.global.in
index bdf394b..218c65a 100644
*** a/src/Makefile.global.in
--- b/src/Makefile.global.in
*************** BITCODE_CXXFLAGS = @BITCODE_CXXFLAGS@
*** 241,246 ****
--- 241,247 ----

  CPP = @CPP@
  CPPFLAGS = @CPPFLAGS@
+ PG_SYSROOT = @PG_SYSROOT@

  override CPPFLAGS := $(ICU_CFLAGS) $(CPPFLAGS)

diff --git a/src/template/darwin b/src/template/darwin
index 159d8bb..c05adca 100644
*** a/src/template/darwin
--- b/src/template/darwin
***************
*** 3,16 ****
  # Note: Darwin is the original code name for macOS, also known as OS X.
  # We still use "darwin" as the port name, partly because config.guess does.

! # Some configure tests require explicit knowledge of where the Xcode "sysroot"
! # is.  We try to avoid having this leak into configure's results, though.
  if test x"$PG_SYSROOT" = x"" ; then
    PG_SYSROOT=`xcodebuild -version -sdk macosx Path 2>/dev/null`
  fi
  # Old xcodebuild versions may produce garbage, so validate the result.
  if test x"$PG_SYSROOT" != x"" ; then
!   if test \! -d "$PG_SYSROOT" ; then
      PG_SYSROOT=""
    fi
  fi
--- 3,17 ----
  # Note: Darwin is the original code name for macOS, also known as OS X.
  # We still use "darwin" as the port name, partly because config.guess does.

! # Select where system include files should be sought.
  if test x"$PG_SYSROOT" = x"" ; then
    PG_SYSROOT=`xcodebuild -version -sdk macosx Path 2>/dev/null`
  fi
  # Old xcodebuild versions may produce garbage, so validate the result.
  if test x"$PG_SYSROOT" != x"" ; then
!   if test -d "$PG_SYSROOT" ; then
!     CPPFLAGS="-isysroot $PG_SYSROOT $CPPFLAGS"
!   else
      PG_SYSROOT=""
    fi
  fi