strip: Don't generate empty output file when nothing to do.

If there was nothing to do strip would skip generating a separate
debug file if one was requested, but it would also not finish the
creation of a new output file (with the non-stripped sections).
Also if there was an error any partially created output would be kept.

Make sure that when the -o output file option is given we always generate
a complete output file (except on error). Also make sure that when the -f
debug file option is given it is only generated when it is not empty.

Add testcase run-strip-nothing.sh that tests the various combinations.

https://sourceware.org/bugzilla/show_bug.cgi?id=21522

Signed-off-by: Mark Wielaard <mark@klomp.org>

5 files changed, 95 insertions, 12 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 6ac0ef2d..e19122e8 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,9 @@
+2017-06-07  Mark Wielaard  <mark@klomp.org>
+
+	* strip.c (handle_elf): Introduce new handle_elf boolean. Use it to
+	determine whether to create an output and/or debug file. Remove new
+	output file on error.
+
 2017-06-06  Mark Wielaard  <mark@klomp.org>
 
 	* strip.c (handle_elf): Assume e_shstrndx section can be removed.
diff --git a/src/strip.c b/src/strip.c
index 11b2a379..2bf95f90 100644
--- a/src/strip.c
+++ b/src/strip.c
@@ -1063,15 +1063,17 @@ handle_elf (int fd, Elf *elf, const char *prefix, const char *fname,
 	shdr_info[cnt].se = dwelf_strtab_add (shst, shdr_info[cnt].name);
       }
 
-  /* Test whether we are doing anything at all.  */
-  if (cnt == idx
-      || (cnt == idx + 1 && shdr_info[ehdr->e_shstrndx].idx == 0))
-    /* Nope, all removable sections are already gone.  Or the only section
-       we would remove is the .shstrtab section which we will add again.  */
-    goto fail_close;
-
-  /* Create the reference to the file with the debug info.  */
-  if (debug_fname != NULL && !remove_shdrs)
+  /* Test whether we are doing anything at all.  Either all removable
+     sections are already gone.  Or the only section we would remove is
+     the .shstrtab section which we would add again.  */
+  bool removing_sections = !(cnt == idx
+			     || (cnt == idx + 1
+				 && shdr_info[ehdr->e_shstrndx].idx == 0));
+  if (output_fname == NULL && !removing_sections)
+      goto fail_close;
+
+  /* Create the reference to the file with the debug info (if any).  */
+  if (debug_fname != NULL && !remove_shdrs && removing_sections)
     {
       /* Add the section header string table section name.  */
       shdr_info[cnt].se = dwelf_strtab_add_len (shst, ".gnu_debuglink", 15);
@@ -1759,7 +1761,8 @@ handle_elf (int fd, Elf *elf, const char *prefix, const char *fname,
   /* Remove any relocations between debug sections in ET_REL
      for the debug file when requested.  These relocations are always
      zero based between the unallocated sections.  */
-  if (debug_fname != NULL && reloc_debug && ehdr->e_type == ET_REL)
+  if (debug_fname != NULL && removing_sections
+      && reloc_debug && ehdr->e_type == ET_REL)
     {
       scn = NULL;
       cnt = 0;
@@ -1997,7 +2000,7 @@ handle_elf (int fd, Elf *elf, const char *prefix, const char *fname,
 
   /* Now that we have done all adjustments to the data,
      we can actually write out the debug file.  */
-  if (debug_fname != NULL)
+  if (debug_fname != NULL && removing_sections)
     {
       /* Finally write the file.  */
       if (unlikely (elf_update (debugelf, ELF_C_WRITE) == -1))
@@ -2230,7 +2233,11 @@ cannot set access and modification date of '%s'"),
 
   /* Close the file descriptor if we created a new file.  */
   if (output_fname != NULL)
-    close (fd);
+    {
+      close (fd);
+      if (result != 0)
+       unlink (output_fname);
+    }
 
   return result;
 }
diff --git a/tests/ChangeLog b/tests/ChangeLog
index a7b20224..ecf62630 100644
--- a/tests/ChangeLog
+++ b/tests/ChangeLog
@@ -1,3 +1,9 @@
+2017-06-07  Mark Wielaard  <mark@klomp.org>
+
+	* run-strip-nothing.sh: New test.
+	* Makefile.am (TESTS): Add run-strip-nothing.sh.
+	(EXTRA_DIST): Likewise.
+
 2017-06-06  Mark Wielaard  <mark@klomp.org>
 
 	* run-strip-test.sh: Test strip -g doesn't introduce extra .shstrtab.
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 50648db8..0aa16da1 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -81,6 +81,7 @@ TESTS = run-arextract.sh run-arsymtest.sh newfile test-nlist \
 	run-strip-test3.sh run-strip-test4.sh run-strip-test5.sh \
 	run-strip-test6.sh run-strip-test7.sh run-strip-test8.sh \
 	run-strip-test9.sh run-strip-test10.sh run-strip-test11.sh \
+	run-strip-nothing.sh \
 	run-strip-groups.sh run-strip-reloc.sh run-strip-strmerge.sh \
 	run-strip-nobitsalign.sh \
 	run-unstrip-test.sh run-unstrip-test2.sh run-unstrip-test3.sh \
@@ -175,6 +176,7 @@ EXTRA_DIST = run-arextract.sh run-arsymtest.sh \
 	     run-strip-test4.sh run-strip-test5.sh run-strip-test6.sh \
 	     run-strip-test7.sh run-strip-test8.sh run-strip-groups.sh \
 	     run-strip-test9.sh run-strip-test10.sh run-strip-test11.sh \
+	     run-strip-nothing.sh \
 	     run-strip-strmerge.sh run-strip-nobitsalign.sh \
 	     testfile-nobitsalign.bz2 testfile-nobitsalign.strip.bz2 \
 	     run-strip-reloc.sh hello_i386.ko.bz2 hello_x86_64.ko.bz2 \
diff --git a/tests/run-strip-nothing.sh b/tests/run-strip-nothing.sh
new file mode 100755
index 00000000..e80bd906
--- /dev/null
+++ b/tests/run-strip-nothing.sh
@@ -0,0 +1,62 @@
+#! /bin/sh
+# Copyright (C) 2017 Red Hat, Inc.
+# This file is part of elfutils.
+#
+# This file is free software; you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation; either version 3 of the License, or
+# (at your option) any later version.
+#
+# elfutils is distributed in the hope that it will be useful, but
+# WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+. $srcdir/test-subr.sh
+
+# If there is nothing to strip then -o output should be identical to input.
+# And there should not be an (empty) -f debug file.
+
+tempfiles a.out strip.out debug.out
+
+# Create no-debug a.out.
+echo "int main() { return 1; }" | gcc -xc -
+
+# strip to file
+testrun ${abs_top_builddir}/src/strip -g -o strip.out ||
+  { echo "*** failed to strip -g -o strip.out a.out"; exit -1; }
+
+testrun ${abs_top_builddir}/src/elfcmp a.out strip.out ||
+  { echo "*** failed strip.out different from a.out"; exit -1; }
+
+# strip original
+testrun ${abs_top_builddir}/src/strip -g ||
+  { echo "*** failed to strip -g a.out"; exit -1; }
+
+testrun ${abs_top_builddir}/src/elfcmp strip.out a.out ||
+  { echo "*** failed a.out different from strip.out"; exit -1; }
+
+# strip to file with debug file
+testrun ${abs_top_builddir}/src/strip -g -o strip.out -f debug.out ||
+  { echo "*** failed to strip -g -o strip.out -f debug.out a.out"; exit -1; }
+
+testrun ${abs_top_builddir}/src/elfcmp a.out strip.out ||
+  { echo "*** failed strip.out different from a.out (with debug)"; exit -1; }
+
+test ! -f debug.out ||
+  { echo "*** failed strip.out and debug.out exist"; exit -1; }
+
+# strip original with debug file
+testrun ${abs_top_builddir}/src/strip -g -f debug.out ||
+  { echo "*** failed to strip -g -f debug.out a.out"; exit -1; }
+
+testrun ${abs_top_builddir}/src/elfcmp strip.out a.out ||
+  { echo "*** failed a.out different from strip.out (with debug)"; exit -1; }
+
+test ! -f debug.out ||
+  { echo "*** failed a.out and debug.out exist"; exit -1; }
+
+exit 0