Re: Silence two Clang warnings

[Paul Eggert <eggert@cs.ucla.edu>]

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Part of the attached patch, recently installed into master, would be 
automatically reverted the next time we merged from gnulib, since 
strftime.c is copied from Gnulib. I'm not getting a warning when 
compiling with Clang, so I'm puzzled as to why the patch was needed. 
Here's how I build (on Fedora 25):

./configure --enable-gcc-warnings CC=clang

Fedora 25 is running clang version 3.9.1 (tags/RELEASE_391/final).

Background: I would rather avoid the need for this sort of patch, as we 
shouldn't have to complicate the code just to pacify a Clang false 
alarm. If an older Clang is generating a false alarm, let's just ignore 
the diagnostic. If it's a newer Clang, let's change the options to Clang 
to suppress the diagnostic.


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From e408e9aa030a00cb1a61acdc729e8d6786b25fe3 Mon Sep 17 00:00:00 2001
From: Philipp Stephani <phst@google.com>
Date: Tue, 13 Jun 2017 13:55:44 +0200
Subject: [PATCH] Silence two Clang warnings by introducing additional local
 variables

* lib/strftime.c (libc_hidden_def):
* lib-src/make-docfile.c (put_filename): Introduce local variables to
silence Clang warnings.
---
 lib-src/make-docfile.c |  6 +++++-
 lib/strftime.c         | 27 ++++++++++++++++-----------
 2 files changed, 21 insertions(+), 12 deletions(-)

diff --git a/lib-src/make-docfile.c b/lib-src/make-docfile.c
index 9470bd6..85bcc8b 100644
--- a/lib-src/make-docfile.c
+++ b/lib-src/make-docfile.c
@@ -224,7 +224,11 @@ put_filename (char *filename)
 
   for (tmp = filename; *tmp; tmp++)
     {
-      if (IS_DIRECTORY_SEP (*tmp))
+      /* Use separate variable to silence a Clang warning on macOS.
+         Clang takes offence of the additional set of parantheses
+         generated by the macro.  */
+      bool is_sep = IS_DIRECTORY_SEP (*tmp);
+      if (is_sep)
 	filename = tmp + 1;
     }
 
diff --git a/lib/strftime.c b/lib/strftime.c
index 99bee4e..18c899d 100644
--- a/lib/strftime.c
+++ b/lib/strftime.c
@@ -1123,18 +1123,23 @@ __strftime_internal (STREAM_OR_CHAR_T *s, STRFTIME_ARG (size_t maxsize)
           if (modifier == L_('E'))
             goto bad_format;
 
-          number_value = ns;
-          if (width == -1)
-            width = 9;
-          else
-            {
-              /* Take an explicit width less than 9 as a precision.  */
-              int j;
-              for (j = width; j < 9; j++)
-                number_value /= 10;
-            }
+          {
+            /* Use a new variable here instead of reusing number_value
+               because Clang complains about the self-assignment
+               generated by DO_NUMBER.  */
+            ptrdiff_t n = ns;
+            if (width == -1)
+              width = 9;
+            else
+              {
+                /* Take an explicit width less than 9 as a precision.  */
+                int j;
+                for (j = width; j < 9; j++)
+                  n /= 10;
+              }
 
-          DO_NUMBER (width, number_value);
+            DO_NUMBER (width, n);
+          }
 #endif
 
         case L_('n'):
-- 
2.9.4