Refine the GHCI macro into HAVE[_{INTERNAL, EXTERNAL}]_INTERPRETER

As discussed in #16331, the GHCI macro, defined through 'ghci' flags
in ghc.cabal.in, ghc-bin.cabal.in and ghci.cabal.in, is supposed to indicate
whether GHC is built with support for an internal interpreter, that runs in
the same process. It is however overloaded in a few places to mean
"there is an interpreter available", regardless of whether it's an internal
or external interpreter.

For the sake of clarity and with the hope of more easily being able to
build stage 1 GHCs with external interpreter support, this patch splits
the previous GHCI macro into 3 different ones:

- HAVE_INTERNAL_INTERPRETER: GHC is built with an internal interpreter
- HAVE_EXTERNAL_INTERPRETER: GHC is built with support for external interpreters
- HAVE_INTERPRETER: HAVE_INTERNAL_INTERPRETER || HAVE_EXTERNAL_INTERPRETER

1 files changed, 12 insertions, 1 deletions

diff --git a/compiler/ghc.cabal.in b/compiler/ghc.cabal.in
index e8e6bf7317..e1f0bec2b0 100644
--- a/compiler/ghc.cabal.in
+++ b/compiler/ghc.cabal.in
@@ -25,6 +25,11 @@ Flag ghci
     Default: False
     Manual: True
 
+Flag ext-interp
+    Description: Support external interpreter
+    Default: True
+    Manual: True
+
 Flag stage1
     Description: Is this stage 1?
     Default: False
@@ -90,9 +95,15 @@ Library
                  -Wnoncanonical-monoid-instances
 
     if flag(ghci)
-        CPP-Options: -DGHCI
+        CPP-Options: -DHAVE_INTERNAL_INTERPRETER
         Include-Dirs: ../rts/dist/build @FFIIncludeDir@
 
+    if flag(ext-interp)
+        CPP-Options: -DHAVE_EXTERNAL_INTERPRETER
+
+    if flag(ghci) || flag(ext-interp)
+        CPP-Options: -DHAVE_INTERPRETER
+
     -- sanity-check to ensure not more than one integer flag is set
     if flag(integer-gmp) && flag(integer-simple)
         build-depends: invalid-cabal-flag-settings<0