[dpkg] 126/187: build: Pass --as-needed to the linker for dselect to avoid libstdc++

[Reiner Herrmann]

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deki-guest pushed a commit to branch master
in repository dpkg.

commit 44cfbc4b31de7d3dc3c6471aeaf21768b4dc015a
Author: Guillem Jover <guillem at debian.org>
Date:   Wed Sep 7 04:56:32 2016 +0200

    build: Pass --as-needed to the linker for dselect to avoid libstdc++
    
    We are not really using anything from libstdc++, so let's avoid the
    dependency entirely. This makes this the only frontend not to pull
    in the C++ run-time.
---
 configure.ac        |  1 +
 debian/changelog    |  2 ++
 dselect/Makefile.am |  4 ++++
 m4/dpkg-linker.m4   | 19 +++++++++++++++++++
 4 files changed, 26 insertions(+)

diff --git a/configure.ac b/configure.ac
index 248d0a6..5804498 100644
--- a/configure.ac
+++ b/configure.ac
@@ -36,6 +36,7 @@ DPKG_DIST_CHECK([test "$GMSGFMT" = ":" && test "$USE_NLS" = "yes"],
 AM_PROG_AR
 LT_INIT([disable-shared])
 DPKG_BUILD_SHARED_LIBS
+DPKG_LINKER_AS_NEEDED
 DPKG_LINKER_VERSION_SCRIPT
 
 # Allow compilation without optional programs
diff --git a/debian/changelog b/debian/changelog
index e3535da..5ee6b9e 100644
--- a/debian/changelog
+++ b/debian/changelog
@@ -178,6 +178,8 @@ dpkg (1.18.11) UNRELEASED; urgency=medium
       marked as deprecated by POSIX).
     - Print an actual newline instead of a literal \n in lcov output.
     - Do not honor DPKG_DATADIR on the installed Dpkg module.
+    - Pass --as-needed to the linker for dselect to avoid libstdc++ dependency.
+      Which makes of dselect the only front-end not pulling the C++ run-time.
 
   [ Updated man pages translations ]
   * German (Helge Kreutzmann).
diff --git a/dselect/Makefile.am b/dselect/Makefile.am
index 9c14f86..3c0817c 100644
--- a/dselect/Makefile.am
+++ b/dselect/Makefile.am
@@ -17,6 +17,10 @@ AM_CXXFLAGS = \
 	-fno-rtti \
 	-fno-exceptions \
 	$(nil)
+if HAVE_LINKER_AS_NEEDED
+AM_LDFLAGS = \
+	-Wl,--as-needed
+endif
 
 
 bin_PROGRAMS = dselect
diff --git a/m4/dpkg-linker.m4 b/m4/dpkg-linker.m4
index e068a38..1bb6435 100644
--- a/m4/dpkg-linker.m4
+++ b/m4/dpkg-linker.m4
@@ -23,6 +23,25 @@ AC_DEFUN([DPKG_LINKER_OPTIMIZATIONS], [
   ])
 ])
 
+# DPKG_LINKER_AS_NEEDED
+# ---------------------
+AC_DEFUN([DPKG_LINKER_AS_NEEDED], [
+  AC_CACHE_CHECK([for --as-needed linker flag], [dpkg_cv_linker_as_needed], [
+    save_LDFLAGS=$LDFLAGS
+    LDFLAGS="$LDFLAGS -Wl,--as-needed"
+    AC_LINK_IFELSE([
+      AC_LANG_PROGRAM([], [])
+    ], [
+      dpkg_cv_linker_as_needed=yes
+    ], [
+      dpkg_cv_linker_as_needed=no
+    ])
+    LDFLAGS="$save_LDFLAGS"
+  ])
+  AM_CONDITIONAL([HAVE_LINKER_AS_NEEDED],
+    [test "x$dpkg_cv_linker_as_needed" = "xyes"])
+])
+
 # DPKG_LINKER_VERSION_SCRIPT
 # --------------------------
 AC_DEFUN([DPKG_LINKER_VERSION_SCRIPT], [

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