Allow to build libgccjit with a soname bound to the GCC major version

When configuring GCC with --program-suffix=-$(BASE_VERSION) to allow
installation multiple GCC versions in parallel, the executable of the
driver (gcc-$(BASE_VERSION)) gets recorded in the libgccjit.so.0
library.  Assuming, that you only install the libgccjit.so.0 library
from the newest GCC, you have a libgccjit installed, which always calls
back to the newest installed version of GCC.  I'm not saying that the
ABI is changing, but I'd like to see the libgccjit calling out to the
corresponding compiler, and therefore installing a libgccjit with a
soname that matches the GCC major version.

The downside is having to rebuild packages built against libgccjit with
each major GCC version, but looking at the reverse dependencies, at
least for package builds, only emacs is using libgccjit.

My plan to use this feature is to build a libgccjit0 using the default
GCC (e.g. gcc-14), and a libgccjit15, when building a newer GCC. When
changing the GCC default to 15, building a libgccjit0 from gcc-15, and a
libgccjit14 from gcc-14.

When configuring without --enable-versioned-jit, the behavior is unchanged.

2025-03-13  Matthias Klose  <doko@ubuntu.com>

gcc/
	* configure.ac: Add option --enable-versioned-jit.
	* configure: Regenerate.
	* Makefile.in: Move from jit/Make-lang.in, setting value from
	configure.ac.
	* doc/install.texi: Document option --enable-versioned-jit.

gcc/jit/
	* Make-lang.in (LIBGCCJIT_VERSION_NUM): Move to ../Makefile.in.

gcc/Makefile.in

@@ -1218,6 +1218,7 @@ LANG_CONFIGUREFRAGS  = @all_lang_configurefrags@
 LANG_MAKEFRAGS = @all_lang_makefrags@
 
 # Used by gcc/jit/Make-lang.in
+LIBGCCJIT_VERSION_NUM = @libgccjit_version@
 LD_VERSION_SCRIPT_OPTION = @ld_version_script_option@
 LD_SONAME_OPTION = @ld_soname_option@
 @ENABLE_DARWIN_AT_RPATH_TRUE@DARWIN_RPATH = @rpath

gcc/configure

@@ -636,6 +636,7 @@ CET_HOST_FLAGS
 LD_PICFLAG
 PICFLAG
 enable_default_pie
+libgccjit_version
 enable_host_bind_now
 LIBGDIAGNOSTICS
 enable_libgdiagnostics
@@ -1059,6 +1060,7 @@ enable_libquadmath_support
 with_linker_hash_style
 with_diagnostics_color
 with_diagnostics_urls
+enable_versioned_jit
 enable_default_pie
 enable_cet
 enable_s390_excess_float_precision
@@ -1834,6 +1836,7 @@ Optional Features:
   --enable-host-bind-now  link host code as BIND_NOW
   --disable-libquadmath-support
                           disable libquadmath support for Fortran
+  --enable-versioned-jit  enable versioned libgccjit build
   --enable-default-pie    enable Position Independent Executable as default
   --enable-cet            enable Intel CET in host libraries [default=auto]
   --enable-s390-excess-float-precision
@@ -21477,7 +21480,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 21480 "configure"
+#line 21483 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -21583,7 +21586,7 @@ else
   lt_dlunknown=0; lt_dlno_uscore=1; lt_dlneed_uscore=2
   lt_status=$lt_dlunknown
   cat > conftest.$ac_ext <<_LT_EOF
-#line 21586 "configure"
+#line 21589 "configure"
 #include "confdefs.h"
 
 #if HAVE_DLFCN_H
@@ -34428,6 +34431,23 @@ cat > gcc-driver-name.h <<EOF
 #define GCC_DRIVER_NAME "${target_noncanonical}-gcc-${gcc_driver_version}${exeext}"
 EOF
 
+# Check whether --enable-versioned-jit was given.
+# Check whether --enable-versioned-jit was given.
+if test "${enable_versioned_jit+set}" = set; then :
+  enableval=$enable_versioned_jit; enable_versioned_jit=$enableval
+else
+  enable_versioned_jit=no
+fi
+
+if test x$enable_versioned_jit = xyes ; then
+  libgccjit_version=$gcc_driver_version
+elif test x$enable_versioned_jit = xno ; then
+  libgccjit_version=0
+else
+  as_fn_error $? "bad value ${enableval} given for --enable-versioned-jit option" "$LINENO" 5
+fi
+
+
 # Check whether --enable-default-pie was given.
 # Check whether --enable-default-pie was given.
 if test "${enable_default_pie+set}" = set; then :

gcc/configure.ac

@@ -7704,6 +7704,21 @@ cat > gcc-driver-name.h <<EOF
 #define GCC_DRIVER_NAME "${target_noncanonical}-gcc-${gcc_driver_version}${exeext}"
 EOF
 
+# Check whether --enable-versioned-jit was given.
+AC_ARG_ENABLE(versioned-jit,
+[AS_HELP_STRING([--enable-versioned-jit],
+  [enable versioned libgccjit build])],
+enable_versioned_jit=$enableval,
+enable_versioned_jit=no)
+if test x$enable_versioned_jit = xyes ; then
+  libgccjit_version=$gcc_driver_version
+elif test x$enable_versioned_jit = xno ; then
+  libgccjit_version=0
+else
+  AC_MSG_ERROR(bad value ${enableval} given for --enable-versioned-jit option)
+fi
+AC_SUBST([libgccjit_version])
+
 # Check whether --enable-default-pie was given.
 AC_ARG_ENABLE(default-pie,
 [AS_HELP_STRING([--enable-default-pie],

gcc/doc/install.texi

@@ -1148,6 +1148,10 @@ This option is required when building the libgccjit.so library.
 Contrast with @option{--enable-shared}, which affects @emph{target}
 libraries.
 
+@item --enable-versioned-jit
+Specify that the @samp{libgccjit} library is built with a soname matching
+the GCC major version.
+
 @item --enable-host-pie
 Specify that the @emph{host} executables should be built into
 position-independent executables (with @option{-fPIE} and @option{-pie}),

gcc/jit/Make-lang.in

@@ -40,7 +40,7 @@
 # into the jit rule, but that needs a little bit of work
 # to do the right thing within all.cross.
 
-LIBGCCJIT_VERSION_NUM = 0
+# LIBGCCJIT_VERSION_NUM is set in ../Makefile.in
 LIBGCCJIT_MINOR_NUM = 0
 LIBGCCJIT_RELEASE_NUM = 1