sys-devel/gdb: Fix cross-compiling (properly) and prefix sysroot

https://github.com/gentoo/gentoo/pull/25896 tried to address cross-compiling in
the wrong way by setting the runtime sysroot and the libdir. The build uses the
latter to find dependent libraries by default, a common technique in GNU
software.

This behaviour can be avoided by passing the "without-prefix" configure option
for each library, allowing the runtime sysroot and the libdir to be set as they
should be. Contrary to what you might expect, the sysroot should actually not be
set at all except when building cross-*/gdb, otherwise the paths get double
prefixed at runtime.

gdb's configure script also has a --with-build-sysroot option that should be set
to assist with cross-compiling. This does not influence runtime behaviour.

The includedir for cross-*/gdb has been changed to prevent it from installing
under /usr/${CTARGET}, where installed headers would collide with those from a
cross-compiled sys-devel/gdb build. /usr/include/${CTARGET}/gdb is consistent
with the files we install under /usr/share, as well as the scheme we use for
multilib headers, e.g. /usr/include/i686-pc-linux-gnu.

Closes: https://bugs.gentoo.org/896008
Signed-off-by: James Le Cuirot <chewi@gentoo.org>
Closes: https://github.com/gentoo/gentoo/pull/29819
Signed-off-by: Sam James <sam@gentoo.org>

2 files changed, 22 insertions, 24 deletions

diff --git a/sys-devel/gdb/gdb-13.1.ebuild b/sys-devel/gdb/gdb-13.1-r1.ebuild
index d356d5e3ecab..bc86849c6276 100644
--- a/sys-devel/gdb/gdb-13.1.ebuild
+++ b/sys-devel/gdb/gdb-13.1-r1.ebuild
@@ -160,21 +160,13 @@ src_configure() {
 		# But the check does not quite work on i686: bug #760926.
 		$(use_enable cet)
 
-		# We need to set both configure options, --with-sysroot and --libdir,
-		# to fix cross build issues that happen when configuring gmp.
-		# We explicitly need --libdir. Having only --with-sysroot without
-		# --libdir would not fix the build issues.
-		# For some reason, it is not enough to set only --with-sysroot,
-		# also not enough to pass --with-gmp-xxx options.
-		--with-sysroot="${ESYSROOT}"
-		--libdir="${ESYSROOT}/usr/$(get_libdir)"
+		# Helps when cross-compiling. Not to be confused with --with-sysroot.
+		--with-build-sysroot="${ESYSROOT}"
 	)
 
-	local sysroot="${EPREFIX}/usr/${CTARGET}"
-
 	is_cross && myconf+=(
-		--with-sysroot="${sysroot}"
-		--includedir="${sysroot}/usr/include"
+		--with-sysroot="\${prefix}/${CTARGET}"
+		--includedir="\${prefix}/include/${CTARGET}"
 		--with-gdb-datadir="\${datadir}/gdb/${CTARGET}"
 	)
 
@@ -211,6 +203,13 @@ src_configure() {
 		$(use_with xxhash)
 		$(use_with guile)
 		$(use_with zstd)
+
+		# Find libraries using the toolchain sysroot rather than the configured
+		# prefix. Needed when cross-compiling.
+		#
+		# Check which libraries to apply this to with:
+		# "${S}"/gdb/configure --help | grep without-lib | sort
+		--without-lib{babeltrace,expat,gmp,iconv,ipt,lzma,mpfr,xxhash}-prefix
 	)
 
 	if use sparc-solaris || use x86-solaris ; then
diff --git a/sys-devel/gdb/gdb-9999.ebuild b/sys-devel/gdb/gdb-9999.ebuild
index d356d5e3ecab..bc86849c6276 100644
--- a/sys-devel/gdb/gdb-9999.ebuild
+++ b/sys-devel/gdb/gdb-9999.ebuild
@@ -160,21 +160,13 @@ src_configure() {
 		# But the check does not quite work on i686: bug #760926.
 		$(use_enable cet)
 
-		# We need to set both configure options, --with-sysroot and --libdir,
-		# to fix cross build issues that happen when configuring gmp.
-		# We explicitly need --libdir. Having only --with-sysroot without
-		# --libdir would not fix the build issues.
-		# For some reason, it is not enough to set only --with-sysroot,
-		# also not enough to pass --with-gmp-xxx options.
-		--with-sysroot="${ESYSROOT}"
-		--libdir="${ESYSROOT}/usr/$(get_libdir)"
+		# Helps when cross-compiling. Not to be confused with --with-sysroot.
+		--with-build-sysroot="${ESYSROOT}"
 	)
 
-	local sysroot="${EPREFIX}/usr/${CTARGET}"
-
 	is_cross && myconf+=(
-		--with-sysroot="${sysroot}"
-		--includedir="${sysroot}/usr/include"
+		--with-sysroot="\${prefix}/${CTARGET}"
+		--includedir="\${prefix}/include/${CTARGET}"
 		--with-gdb-datadir="\${datadir}/gdb/${CTARGET}"
 	)
 
@@ -211,6 +203,13 @@ src_configure() {
 		$(use_with xxhash)
 		$(use_with guile)
 		$(use_with zstd)
+
+		# Find libraries using the toolchain sysroot rather than the configured
+		# prefix. Needed when cross-compiling.
+		#
+		# Check which libraries to apply this to with:
+		# "${S}"/gdb/configure --help | grep without-lib | sort
+		--without-lib{babeltrace,expat,gmp,iconv,ipt,lzma,mpfr,xxhash}-prefix
 	)
 
 	if use sparc-solaris || use x86-solaris ; then