stdbuf: A new program to run a command with modified stdio buffering

* AUTHORS: Register as the author.
* NEWS: Mention this change.
* README: Add stdbuf command to list.
* configure.ac: Only enable on ELF systems with GCC.
* cfg.mk (sc_system_h_headers): Use VC_LIST_EXCEPT rather than
VC_LIST, so we can add an exception, if needed.
* .x-sc_system_h_headers: New file.  Exempt libstdbuf.c.
* Makefile.am (syntax_check_exceptions): Add .x-sc_system_h_headers.
* doc/coreutils.texi (stdbuf invocation): Add stdbuf info.
* man/.gitignore: Ignore generated manpage.
* src/.gitignore: Ignore stdbuf and libstdbuf.so binaries.
* man/Makefile.am (stdbuf.1): Add dependency.
* man/stdbuf.x: New file with example usage.
* po/POTFILES.in: Reference new command and shared library sources.
* src/Makefile.am (build_if_possible__progs): Add stdbuf and libstdbuf,
(pkglib_PROGRAMS): Reference optional shared lib,
(libstdbuf_so_LDADD): Ensure we don't link with non PIC libcoreutils.a.
(libstdbuf_so_LDFLAGS): Add -shared GCC option,
(libstdbuf_so_CFLAGS): Add -fPIC GCC option.
(check-README): Exclude libstbuf.
(check-AUTHORS): ditto.
(sc_tight_scope): Exclude functions starting with __.
* src/libstdbuf.c: The LD_PRELOAD shared library to control buffering.
* src/stdbuf.c: New file to setup env variables before execing command.
* tests/Makefile.am: Reference new test file.
* tests/misc/help-version: Set expected exit codes.
* tests/misc/invalid-opt: ditto.
* tests/misc/stdbuf: Add 9 tests.

1 files changed, 21 insertions, 3 deletions

diff --git a/src/Makefile.am b/src/Makefile.am
index 3bed7b1af..4f21c8633 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -24,7 +24,7 @@ no_install__progs = \
   arch hostname su
 
 build_if_possible__progs = \
-  chroot df hostid nice pinky stty su uname uptime users who
+  chroot df hostid nice pinky stdbuf libstdbuf.so stty su uname uptime users who
 
 AM_CFLAGS = $(WARN_CFLAGS) $(WERROR_CFLAGS)
 
@@ -48,6 +48,8 @@ bin_PROGRAMS = $(OPTIONAL_BIN_PROGS)
 
 noinst_PROGRAMS = setuidgid getlimits
 
+pkglib_PROGRAMS = $(OPTIONAL_PKGLIB_PROGS)
+
 noinst_HEADERS = \
   chown-core.h \
   copy.h \
@@ -91,6 +93,7 @@ du_LDADD = $(LDADD)
 getlimits_LDADD = $(LDADD)
 ptx_LDADD = $(LDADD)
 split_LDADD = $(LDADD)
+stdbuf_LDADD = $(LDADD)
 timeout_LDADD = $(LDADD)
 truncate_LDADD = $(LDADD)
 
@@ -170,6 +173,7 @@ du_LDADD += $(LIBICONV)
 getlimits_LDADD += $(LIBICONV)
 ptx_LDADD += $(LIBICONV)
 split_LDADD += $(LIBICONV)
+stdbuf_LDADD += $(LIBICONV)
 timeout_LDADD += $(LIBICONV)
 truncate_LDADD += $(LIBICONV)
 
@@ -286,6 +290,16 @@ sha512sum_CPPFLAGS = -DHASH_ALGO_SHA512=1 $(AM_CPPFLAGS)
 
 ginstall_CPPFLAGS = -DENABLE_MATCHPATHCON=1 $(AM_CPPFLAGS)
 
+# Ensure we don't link against libcoreutils.a as that lib is
+# not compiled with -fPIC which causes issues on 64 bit at least
+libstdbuf_so_LDADD =
+
+# Note libstdbuf is only compiled if GCC is available
+# (as per the check in configure.ac), so these flags should be available.
+# libtool is probably required to relax this dependency.
+libstdbuf_so_LDFLAGS = -shared
+libstdbuf_so_CFLAGS = -fPIC $(AM_CFLAGS)
+
 editpl = sed -e 's,@''PERL''@,$(PERL),g'
 
 BUILT_SOURCES += dircolors.h
@@ -369,6 +383,7 @@ check-README:
 	rm -rf $(pr) $(pm)
 	echo $(all_programs) \
 	 | tr -s ' ' '\n' | sed -e 's,$(EXEEXT)$$,,;s/ginstall/install/' \
+	 | sed /libstdbuf/d \
 	 | $(ASSORT) -u > $(pm) && \
 	sed -n '/^The programs .* are:/,/^[a-zA-Z]/p' $(top_srcdir)/README \
 	  | sed -n '/^   */s///p' | tr -s ' ' '\n' > $(pr)
@@ -394,6 +409,7 @@ check-AUTHORS: $(all_programs)
 	  && { echo "$@: skipping this check"; exit 0; }; \
 	rm -f $(au_actual) $(au_dotdot);		\
 	for i in `ls $(all_programs) | sed -e 's,$(EXEEXT)$$,,' \
+	    | sed /libstdbuf/d				\
 	    | $(ASSORT) -u`; do				\
 	  test "$$i" = '[' && continue;			\
 	  exe=$$i;					\
@@ -416,7 +432,9 @@ check-AUTHORS: $(all_programs)
 # Most functions in src/*.c should have static scope.
 # Any that don't must be marked with `extern', but `main'
 # and `usage' are exceptions.  They're always extern, but
-# don't need to be marked.
+# don't need to be marked. Also functions starting with __
+# are exempted due to possibly being added by the compiler
+# (when compiled as a shared library for example).
 #
 # The second nm|grep checks for file-scope variables with `extern' scope.
 .PHONY: sc_tight_scope
@@ -427,7 +445,7 @@ sc_tight_scope: $(bin_PROGRAMS)
 	       test -f $$f && d= || d=$(srcdir)/; echo $$d$$f; done`;	\
 	hdr=`for f in $(noinst_HEADERS); do				\
 	       test -f $$f && d= || d=$(srcdir)/; echo $$d$$f; done`;	\
-	( printf 'main\nusage\n';					\
+	( printf 'main\nusage\n_.*\n';					\
 	  grep -h -A1 '^extern .*[^;]$$' $$src				\
 	    | grep -vE '^(extern |--)' | sed 's/ .*//';			\
 	  perl -ne '/^extern \S+ (\S*) \(/ and print "$$1\n"' $$hdr;	\