configure: Avoid hard-coded ld path on Windows

The fix to #17962 ended up regressing on Windows as it failed to
replicate the logic responsible for overriding the toolchain paths on
Windows. This resulted in a hard-coded path to a directory that likely
doesn't exist on the user's system (#18550).

(cherry picked from commit 34e0fa963f35a77093fc7111a80c557fc6bd614f)

7 files changed, 45 insertions, 24 deletions

diff --git a/aclocal.m4 b/aclocal.m4
index 6f54eeff1f..ead8cebc00 100644
--- a/aclocal.m4
+++ b/aclocal.m4
@@ -516,6 +516,10 @@ AC_DEFUN([FP_SETTINGS],
         SettingsHaskellCPPCommand="${mingw_bin_prefix}gcc.exe"
         SettingsHaskellCPPFlags="$HaskellCPPArgs"
         SettingsLdCommand="${mingw_bin_prefix}ld.exe"
+        # Overrides FIND_MERGE_OBJECTS in order to avoid hard-coding linker
+        # path on Windows (#18550).
+        SettingsMergeObjectsCommand="${SettingsLdCommand}"
+        SettingsMergeObjectsFlags="-r --oformat=pe-bigobj-x86-64"
         SettingsArCommand="${mingw_bin_prefix}ar.exe"
         SettingsRanlibCommand="${mingw_bin_prefix}ranlib.exe"
         SettingsDllWrapCommand="${mingw_bin_prefix}dllwrap.exe"
@@ -529,6 +533,8 @@ AC_DEFUN([FP_SETTINGS],
         SettingsHaskellCPPCommand="$(basename $HaskellCPPCmd)"
         SettingsHaskellCPPFlags="$HaskellCPPArgs"
         SettingsLdCommand="$(basename $LdCmd)"
+        SettingsMergeObjectsCommand="$(basename $MergeObjsCmd)"
+        SettingsMergeObjectsFlags="$MergeObjsArgs"
         SettingsArCommand="$(basename $ArCmd)"
         SettingsDllWrapCommand="$(basename $DllWrapCmd)"
         SettingsWindresCommand="$(basename $WindresCmd)"
@@ -538,6 +544,8 @@ AC_DEFUN([FP_SETTINGS],
         SettingsHaskellCPPCommand="$HaskellCPPCmd"
         SettingsHaskellCPPFlags="$HaskellCPPArgs"
         SettingsLdCommand="$LdCmd"
+        SettingsMergeObjectsCommand="$MergeObjsCmd"
+        SettingsMergeObjectsFlags="$MergeObjsArgs"
         SettingsArCommand="$ArCmd"
         SettingsRanlibCommand="$RanlibCmd"
         if test -z "$DllWrapCmd"
@@ -592,6 +600,8 @@ AC_DEFUN([FP_SETTINGS],
     AC_SUBST(SettingsCCompilerSupportsNoPie)
     AC_SUBST(SettingsLdCommand)
     AC_SUBST(SettingsLdFlags)
+    AC_SUBST(SettingsMergeObjectsCommand)
+    AC_SUBST(SettingsMergeObjectsFlags)
     AC_SUBST(SettingsArCommand)
     AC_SUBST(SettingsRanlibCommand)
     AC_SUBST(SettingsDllWrapCommand)
@@ -2605,7 +2615,7 @@ AC_DEFUN([CHECK_FOR_GOLD_T22266],[
         ])
 
         $CC -c -o conftest.a.o conftest.a.c || AC_MSG_ERROR([Failed to compile test])
-        $SettingsMergeObjectsCommand $SettingsMergeObjectsFlags -T conftest.t conftest.a.o -o conftest.ar.o || AC_MSG_ERROR([Failed to merge test object])
+        $MergeObjsCmd $MergeObjsArgs -T conftest.t conftest.a.o -o conftest.ar.o || AC_MSG_ERROR([Failed to merge test object])
 
         $CC -c -o conftest.main.o conftest.main.c || AC_MSG_ERROR([Failed to compile test driver])
         $CC conftest.ar.o conftest.main.o -o conftest || AC_MSG_ERROR([Failed to link test driver])
@@ -2625,33 +2635,30 @@ AC_DEFUN([CHECK_FOR_GOLD_T22266],[
 # ------------------
 # Find which linker to use to merge object files.
 #
+# See Note [Merging object files for GHCi] in GHC.Driver.Pipeline.
 AC_DEFUN([FIND_MERGE_OBJECTS],[
     AC_REQUIRE([FIND_LD])
 
-    if test -z "$SettingsMergeObjectsCommand"; then
-        SettingsMergeObjectsCommand="$LD"
+    if test -z "$MergeObjsCmd"; then
+        MergeObjsCmd="$LD"
     fi
-    if test -z "$SettingsMergeObjectsFlags"; then
-        SettingsMergeObjectsFlags="-r"
+    if test -z "$MergeObjsArgs"; then
+        MergeObjsArgs="-r"
     fi
 
-    CHECK_FOR_GOLD_T22266($SettingsMergeObjectsCommand)
+    CHECK_FOR_GOLD_T22266($MergeObjsCmd)
     if test "$result" = "1"; then
-        AC_MSG_NOTICE([$SettingsMergeObjectsCommand is broken due to binutils 22266, looking for another linker...])
-        SettingsMergeObjectsCommand=""
-        AC_CHECK_TARGET_TOOL([SettingsMergeObjectsCommand], [ld])
-        CHECK_FOR_GOLD_T22266($SettingsMergeObjectsCommand)
+        AC_MSG_NOTICE([$MergeObjsCmd is broken due to binutils 22266, looking for another linker...])
+        MergeObjsCmd=""
+        AC_CHECK_TARGET_TOOL([MergeObjsCmd], [ld])
+        CHECK_FOR_GOLD_T22266($MergeObjsCmd)
         if test "$result" = "1"; then
-            AC_MSG_ERROR([Linker is affected by binutils 22266 but couldn't find another unaffected linker. Please set the SettingsMergeObjectsCommand variable to a functional linker.])
+            AC_MSG_ERROR([Linker is affected by binutils 22266 but couldn't find another unaffected linker. Please set the MergeObjsCmd variable to a functional linker.])
         fi
     fi
 
-    if test "$windows" = YES -a "$EnableDistroToolchain" = "NO" -a "$WORD_SIZE" = 64; then
-        SettingsMergeObjectsFlags="$SettingsMergeObjectsFlags --oformat=pe-bigobj-x86-64"
-    fi
-
-    AC_SUBST(SettingsMergeObjectsCommand)
-    AC_SUBST(SettingsMergeObjectsFlags)
+    AC_SUBST([MergeObjsCmd])
+    AC_SUBST([MergeObjsArgs])
 ])
 
 # FIND_PYTHON
diff --git a/compiler/GHC/Settings/IO.hs b/compiler/GHC/Settings/IO.hs
index 99e7672e8e..75f0bcca0e 100644
--- a/compiler/GHC/Settings/IO.hs
+++ b/compiler/GHC/Settings/IO.hs
@@ -138,7 +138,7 @@ initSettings top_dir = do
         as_args  = map Option cc_args
         ld_prog  = cc_prog
         ld_args  = map Option (cc_args ++ words cc_link_args_str)
-  ld_r_prog <- getSetting "Merge objects command"
+  ld_r_prog <- getToolSetting "Merge objects command"
   ld_r_args <- getSetting "Merge objects flags"
 
   llvmTarget <- getSetting "LLVM target"
diff --git a/configure.ac b/configure.ac
index e92b2dc2f4..285740f3f6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -448,6 +448,8 @@ then
     NM="${mingwbin}nm.exe"
     RANLIB="${mingwbin}ranlib.exe"
     OBJDUMP="${mingwbin}objdump.exe"
+    MergeObjsCmd="$LD"
+    MergeObjsArgs="-r --oformat=pe-bigobj-x86-64"
     fp_prog_ar="${mingwbin}ar.exe"
 
     AC_PATH_PROG([Genlib],[genlib])
diff --git a/hadrian/cfg/system.config.in b/hadrian/cfg/system.config.in
index 7fba53f43e..fbbb2099b6 100644
--- a/hadrian/cfg/system.config.in
+++ b/hadrian/cfg/system.config.in
@@ -14,6 +14,7 @@ hs-cpp         = @HaskellCPPCmd@
 ld             = @LdCmd@
 make           = @MakeCmd@
 nm             = @NmCmd@
+merge-objects  = @MergeObjsCmd@
 objdump        = @ObjdumpCmd@
 ranlib         = @REAL_RANLIB_CMD@
 sphinx-build   = @SPHINXBUILD@
@@ -115,10 +116,10 @@ conf-ld-linker-args-stage1  = @CONF_LD_LINKER_OPTS_STAGE1@
 conf-ld-linker-args-stage2  = @CONF_LD_LINKER_OPTS_STAGE2@
 conf-ld-linker-args-stage3  = @CONF_LD_LINKER_OPTS_STAGE3@
 
-conf-merge-objects-args-stage0  = @SettingsMergeObjectsFlags@
-conf-merge-objects-args-stage1  = @SettingsMergeObjectsFlags@
-conf-merge-objects-args-stage2  = @SettingsMergeObjectsFlags@
-conf-merge-objects-args-stage3  = @SettingsMergeObjectsFlags@
+conf-merge-objects-args-stage0  = @MergeObjsArgs@
+conf-merge-objects-args-stage1  = @MergeObjsArgs@
+conf-merge-objects-args-stage2  = @MergeObjsArgs@
+conf-merge-objects-args-stage3  = @MergeObjsArgs@
 
 
 # Settings:
diff --git a/hadrian/src/Builder.hs b/hadrian/src/Builder.hs
index 7624ae91ad..0187fdd724 100644
--- a/hadrian/src/Builder.hs
+++ b/hadrian/src/Builder.hs
@@ -312,7 +312,7 @@ systemBuilderPath builder = case builder of
     Happy           -> fromKey "happy"
     HsCpp           -> fromKey "hs-cpp"
     Ld _            -> fromKey "ld"
-    MergeObjects _  -> fromKey "settings-merge-objects-command"
+    MergeObjects _  -> fromKey "merge-objects"
     Make _          -> fromKey "make"
     Makeinfo        -> fromKey "makeinfo"
     Nm              -> fromKey "nm"
diff --git a/mk/config.mk.in b/mk/config.mk.in
index 77da4d86bd..7828ead3ea 100644
--- a/mk/config.mk.in
+++ b/mk/config.mk.in
@@ -544,6 +544,16 @@ LD_STAGE1       = $(LD)
 LD_STAGE2       = $(LD)
 LD_STAGE3       = $(LD)
 
+MERGE_OBJS_STAGE0 = @MergeObjsCmd@
+MERGE_OBJS_STAGE1 = @MergeObjsCmd@
+MERGE_OBJS_STAGE2 = @MergeObjsCmd@
+MERGE_OBJS_STAGE3 = @MergeObjsCmd@
+
+MERGE_OBJS_STAGE0_FLAGS = @MergeObjsArgs@
+MERGE_OBJS_STAGE1_FLAGS = @MergeObjsArgs@
+MERGE_OBJS_STAGE2_FLAGS = @MergeObjsArgs@
+MERGE_OBJS_STAGE3_FLAGS = @MergeObjsArgs@
+
 # Cross-compiling options
 # See Note [CrossCompiling vs Stage1Only]
 CrossCompiling        = @CrossCompiling@
diff --git a/rules/build-package-way.mk b/rules/build-package-way.mk
index a2a1e9a8fe..c1b95032ac 100644
--- a/rules/build-package-way.mk
+++ b/rules/build-package-way.mk
@@ -107,6 +107,7 @@ endif
 endif
 
 # Build the GHCi library
+# See Note [Merging object files for GHCi] in GHC.Driver.Pipeline.
 ifneq "$(filter $3, v p)" ""
 $1_$2_$3_GHCI_LIB = $1/$2/build/HS$$($1_$2_COMPONENT_ID).$$($3_osuf)
 ifeq "$$($1_$2_BUILD_GHCI_LIB)" "YES"
@@ -116,7 +117,7 @@ BINDIST_LIBS += $$($1_$2_$3_GHCI_LIB)
 endif
 endif
 $$($1_$2_$3_GHCI_LIB) : $$($1_$2_$3_HS_OBJS) $$($1_$2_$3_CMM_OBJS) $$($1_$2_$3_C_OBJS) $$($1_$2_$3_S_OBJS) $$($1_$2_EXTRA_OBJS) $$($1_$2_LD_SCRIPT)
-	$$(call cmd,SettingsMergeObjectsCommand) $(SettingsMergeObjectsFlags) $$(if $$($1_$2_LD_SCRIPT),$$($1_$2_LD_SCRIPT_CMD) $$($1_$2_LD_SCRIPT)) -o $$@ $$(EXTRA_LD_LINKER_OPTS) $$($1_$2_$3_HS_OBJS) $$($1_$2_$3_CMM_OBJS) $$($1_$2_$3_C_OBJS) $$($1_$2_$3_S_OBJS) $$($1_$2_EXTRA_OBJS)
+	$$(call cmd,MERGE_OBJS_STAGE$4) $(MERGE_OBJS_STAGE$4_FLAGS) $$(if $$($1_$2_LD_SCRIPT),$$($1_$2_LD_SCRIPT_CMD) $$($1_$2_LD_SCRIPT)) -o $$@ $$(EXTRA_LD_LINKER_OPTS) $$($1_$2_$3_HS_OBJS) $$($1_$2_$3_CMM_OBJS) $$($1_$2_$3_C_OBJS) $$($1_$2_$3_S_OBJS) $$($1_$2_EXTRA_OBJS)
 ifeq "$$($1_$2_BUILD_GHCI_LIB)" "YES"
 # Don't bother making ghci libs for bootstrapping packages
 ifneq "$4" "0"