gnu: diffutils: Fix signal processing.

diffutils has a race condition in its signal processing code which is easy to
trigger on powerpc64le-linux.  More often than not, it causes the ‘colors’
test to fail and therefore the build of the package fails as well.

Add the patch proposed in Debian bug 922552 which fixes the problem.

* gnu/packages/patches/diffutils-fix-signal-processing.patch: New file.
* gnu/local.mk (dist_patch_DATA): Add it.
* gnu/packages/base.scm (diffutils)[source]: Use it.

Signed-off-by: Maxim Cournoyer <maxim.cournoyer@gmail.com>

gnu/local.mk

@@ -1002,6 +1002,7 @@ dist_patch_DATA =						\
   %D%/packages/patches/desmume-gcc7-fixes.patch			\
   %D%/packages/patches/dfu-programmer-fix-libusb.patch		\
   %D%/packages/patches/diffoscope-fix-llvm-test.patch		\
+  %D%/packages/patches/diffutils-fix-signal-processing.patch	\
   %D%/packages/patches/diffutils-gets-undeclared.patch		\
   %D%/packages/patches/dkimproxy-add-ipv6-support.patch		\
   %D%/packages/patches/docbook-xsl-nonrecursive-string-subst.patch	\

gnu/packages/base.scm

@@ -274,7 +274,8 @@ (define-public diffutils
             (sha256
              (base32
               "09isrg0isjinv8c535nxsi1s86wfdfzml80dbw41dj9x3hiad9xk"))
-            (patches (search-patches "coreutils-gnulib-tests.patch"))))
+            (patches (search-patches "coreutils-gnulib-tests.patch"
+                                     "diffutils-fix-signal-processing.patch"))))
    (build-system gnu-build-system)
    (native-inputs (list perl))
    (synopsis "Comparing and merging files")

gnu/packages/patches/diffutils-fix-signal-processing.patch

@@ -0,0 +1,58 @@
+Author: Frédéric Bonnard <frediz@debian.org>
+
+Obtained from:
+
+https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=922552#19
+
+Fixes bug reported upstream at:
+
+https://debbugs.gnu.org/cgi/bugreport.cgi?bug=34519
+
+diff --git a/src/diff.c b/src/diff.c
+index e2eb32437353..b574e8282dc9 100644
+--- a/src/diff.c
++++ b/src/diff.c
+@@ -1451,6 +1451,8 @@ compare_files (struct comparison const *parent,
+ 	}
+     }
+ 
++  final_process_signals ();
++
+   /* Now the comparison has been done, if no error prevented it,
+      and STATUS is the value this function will return.  */
+ 
+diff --git a/src/diff.h b/src/diff.h
+index 03daaa4a0530..e177fe600a25 100644
+--- a/src/diff.h
++++ b/src/diff.h
+@@ -390,6 +390,7 @@ extern enum changes analyze_hunk (struct change *, lin *, lin *, lin *, lin *);
+ extern void begin_output (void);
+ extern void debug_script (struct change *);
+ extern void fatal (char const *) __attribute__((noreturn));
++extern void final_process_signals (void);
+ extern void finish_output (void);
+ extern void message (char const *, char const *, char const *);
+ extern void message5 (char const *, char const *, char const *,
+diff --git a/src/util.c b/src/util.c
+index 4f4d9bb285eb..56d292de2927 100644
+--- a/src/util.c
++++ b/src/util.c
+@@ -237,6 +237,18 @@ process_signals (void)
+     }
+ }
+ 
++/* Process remaining signals once before exit  */
++void
++final_process_signals (void)
++{
++  static int last = 1;
++
++  if (last) {
++    process_signals ();
++    last = 0;
++  }
++}
++
+ static void
+ install_signal_handlers (void)
+ {