[PATCH 1/4] config: Add top-level flag to disable host PCH.

Iain Sandoe iains.gcc@gmail.com
Thu Nov 4 20:02:15 GMT 2021


This provides a --disable-host-pch-support configure flag
that is passed down to libcpp, gcc and libstdc++ where the
support for PCH is enacted.

Signed-off-by: Iain Sandoe <iain@sandoe.co.uk>

ChangeLog:

	* Makefile.def: Pass host PCH support configuration
	to libcpp, gcc and libstdc++.
	* Makefile.in: Regenerate.
	* configure: Regenerate.
	* configure.ac: Add --disable-host-pch-support flag.
	* doc/install.texi: Document the option.
---
 Makefile.def         |  9 +++--
 Makefile.in          | 87 +++++++++++++++++++++++++++++---------------
 configure            | 42 +++++++++++++++++++++
 configure.ac         | 35 ++++++++++++++++++
 gcc/doc/install.texi |  6 +++
 5 files changed, 146 insertions(+), 33 deletions(-)

diff --git a/Makefile.def b/Makefile.def
index 0abc42b1a1b..671d1c7ccc6 100644
--- a/Makefile.def
+++ b/Makefile.def
@@ -47,7 +47,8 @@ host_modules= { module= fixincludes; bootstrap=true;
 host_modules= { module= flex; no_check_cross= true; };
 host_modules= { module= gas; bootstrap=true; };
 host_modules= { module= gcc; bootstrap=true; 
-		extra_make_flags="$(EXTRA_GCC_FLAGS)"; };
+		extra_make_flags="$(EXTRA_GCC_FLAGS)";
+		extra_configure_flags="@configure_host_pch_support@"; };
 host_modules= { module= gmp; lib_path=.libs; bootstrap=true;
 		// Work around in-tree gmp configure bug with missing flex.
 		extra_configure_flags='--disable-shared LEX="touch lex.yy.c"';
@@ -81,7 +82,8 @@ host_modules= { module= tcl;
 host_modules= { module= itcl; };
 host_modules= { module= ld; bootstrap=true; };
 host_modules= { module= libbacktrace; bootstrap=true; };
-host_modules= { module= libcpp; bootstrap=true; };
+host_modules= { module= libcpp; bootstrap=true;
+                extra_configure_flags="@configure_host_pch_support@"; };
 // As with libiconv, don't install any of libcody
 host_modules= { module= libcody; bootstrap=true;
 		no_install= true;
@@ -152,7 +154,8 @@ host_modules= { module= libctf; bootstrap=true; };
 target_modules = { module= libstdc++-v3;
 		   bootstrap=true;
 		   lib_path=src/.libs;
-		   raw_cxx=true; };
+		   raw_cxx=true;
+		   extra_configure_flags="@configure_host_pch_support@"; };
 target_modules = { module= libsanitizer;
 		   bootstrap=true;
 		   lib_path=.libs;

diff --git a/configure.ac b/configure.ac
index 550e6993b59..0d9c36bf6d6 100644
--- a/configure.ac
+++ b/configure.ac
@@ -408,6 +408,41 @@ AC_ARG_ENABLE(compressed_debug_sections,
   fi
 ], [enable_compressed_debug_sections=])
 
+# Add a configure option to control whether the host will support pre-compiled
+# headers (PCH) for the c-family compilers.  At present, the default is 'yes'
+# for most platforms but this can be adjusted below for any that are unable to
+# support it.  'configure_host_pch_support' is passed as an additional config
+# arg to the configures for host and target modules that depend on the support
+# where this is not specified explicitly.
+configure_host_pch_support=
+AC_ARG_ENABLE(host_pch_support,
+[AS_HELP_STRING([--disable-host-pch-support],
+                [Disable support for C-family precompiled headers])],
+[
+  ENABLE_HOST_PCH=$enableval
+  case "${host}" in
+    aarch64-*-darwin* | arm64*-*-darwin*)
+      if test "x${ENABLE_HOST_PCH}" = xyes; then
+        AC_MSG_ERROR([PCH is not supported on aarch64/arm64 Darwin hosts])
+      fi
+      ;;
+    *)
+      ;;
+  esac
+],[
+  # The configure line does not specify, so set appropriate values to pass to
+  # module configures that depend on this.
+  case "${host}" in
+    aarch64-*-darwin* | arm64*-*-darwin*)
+      configure_host_pch_support='--enable-host-pch-support=no'
+      ;;
+    *) 
+      configure_host_pch_support='--enable-host-pch-support=yes'
+      ;;
+  esac
+])
+AC_SUBST(configure_host_pch_support)
+
 # Configure extra directories which are host specific
 
 case "${host}" in
diff --git a/gcc/doc/install.texi b/gcc/doc/install.texi
index 094469b9a4e..5581e4cb063 100644
--- a/gcc/doc/install.texi
+++ b/gcc/doc/install.texi
@@ -1015,6 +1015,12 @@ This option is required when building the libgccjit.so library.
 Contrast with @option{--enable-shared}, which affects @emph{target}
 libraries.
 
+@item --disable-host-pch-support
+Specify that the c-family compilers should be built without support for
+Pre-Compiled-Headers (PCH).  The compilers will generate stub pch files
+(to avoid breaking build scripts), but ignore these (or any existing PCH
+files) when searching for headers.
+
 @item @anchor{with-gnu-as}--with-gnu-as
 Specify that the compiler should assume that the
 assembler it finds is the GNU assembler.  However, this does not modify
-- 
2.24.3 (Apple Git-128)



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