build: update to latest gnulib and adapt

Mark functions as pure of const, per recommendations enabled by
new gcc -W options.  Apply _GL_ATTRIBUTE_PURE and _GL_ATTRIBUTE_CONST.
* src/common.h: Apply new function attributes.
* src/pch.c: Likewise.
* src/pch.h: Likewise.
* src/util.c: Likewise.
* src/util.h: Likewise.
* configure.ac: Use -Wno-format-nonliteral.
* m4/.gitignore: Update.
* gnulib: Update to latest.
* cfg.mk: Exempt src/util.c from two tests, to avoid new
"make syntax-check" failures.

5 files changed, 24 insertions, 24 deletions

diff --git a/src/common.h b/src/common.h
index 43919b8..38ecc99 100644
--- a/src/common.h
+++ b/src/common.h
@@ -202,7 +202,7 @@ XTERN lin out_offset;
 XTERN lin last_frozen_line;
 
 bool copy_till (struct outstate *, lin);
-bool similar (char const *, size_t, char const *, size_t);
+bool similar (char const *, size_t, char const *, size_t) _GL_ATTRIBUTE_PURE;
 
 #ifdef ENABLE_MERGE
 enum conflict_style { MERGE_MERGE, MERGE_DIFF3 };
diff --git a/src/pch.c b/src/pch.c
index 6909850..0d0c4b9 100644
--- a/src/pch.c
+++ b/src/pch.c
@@ -315,7 +315,7 @@ there_is_another_patch (bool need_header, mode_t *file_type)
     return true;
 }
 
-static mode_t
+static mode_t _GL_ATTRIBUTE_PURE
 fetchmode (char const *str)
 {
    const char *s;
@@ -366,7 +366,7 @@ sha1_says_nonexistent(char const *sha1, char const *end)
   return s == end;
 }
 
-static char const *
+static char const * _GL_ATTRIBUTE_PURE
 skip_hex_digits (char const *str)
 {
   char const *s;
@@ -2248,7 +2248,7 @@ pch_mode (bool which)
    This accepts just a subset of the valid commands, but it's
    good enough in practice.  */
 
-static char
+static char _GL_ATTRIBUTE_PURE
 get_ed_command_letter (char const *line)
 {
   char const *p = line;
diff --git a/src/pch.h b/src/pch.h
index 6383d85..5e2498b 100644
--- a/src/pch.h
+++ b/src/pch.h
@@ -19,28 +19,28 @@
 
 enum nametype { OLD, NEW, INDEX, NONE };
 
-lin pch_end (void);
-lin pch_first (void);
-lin pch_hunk_beg (void);
-char const *pch_c_function (void);
-char const * pch_timestr (bool which);
-mode_t pch_mode (bool which);
-lin pch_newfirst (void);
-lin pch_prefix_context (void);
-lin pch_ptrn_lines (void);
-lin pch_repl_lines (void);
-lin pch_suffix_context (void);
+lin pch_end (void) _GL_ATTRIBUTE_PURE;
+lin pch_first (void) _GL_ATTRIBUTE_PURE;
+lin pch_hunk_beg (void) _GL_ATTRIBUTE_PURE;
+char const *pch_c_function (void) _GL_ATTRIBUTE_PURE;
+char const * pch_timestr (bool which) _GL_ATTRIBUTE_PURE;
+mode_t pch_mode (bool which) _GL_ATTRIBUTE_PURE;
+lin pch_newfirst (void) _GL_ATTRIBUTE_PURE;
+lin pch_prefix_context (void) _GL_ATTRIBUTE_PURE;
+lin pch_ptrn_lines (void) _GL_ATTRIBUTE_PURE;
+lin pch_repl_lines (void) _GL_ATTRIBUTE_PURE;
+lin pch_suffix_context (void) _GL_ATTRIBUTE_PURE;
 bool pch_swap (void);
 bool pch_write_line (lin, FILE *);
 bool there_is_another_patch (bool, mode_t *);
-char *pfetch (lin);
-char pch_char (lin);
+char *pfetch (lin) _GL_ATTRIBUTE_PURE;
+char pch_char (lin) _GL_ATTRIBUTE_PURE;
 int another_hunk (enum diff, bool);
-int pch_says_nonexistent (bool);
-size_t pch_line_len (lin);
-const char *pch_name(enum nametype);
-bool pch_copy (void);
-bool pch_rename (void);
+int pch_says_nonexistent (bool) _GL_ATTRIBUTE_PURE;
+size_t pch_line_len (lin) _GL_ATTRIBUTE_PURE;
+const char *pch_name(enum nametype) _GL_ATTRIBUTE_PURE;
+bool pch_copy (void) _GL_ATTRIBUTE_PURE;
+bool pch_rename (void) _GL_ATTRIBUTE_PURE;
 void do_ed_script (char const *, char const *, int *, FILE *);
 void open_patch_file (char const *);
 void re_patch (void);
diff --git a/src/util.c b/src/util.c
index 6ffc6cc..71dd004 100644
--- a/src/util.c
+++ b/src/util.c
@@ -123,7 +123,7 @@ file_already_seen (struct stat const *st)
   return hash_lookup (file_id_table, &f) != 0;
 }
 
-static bool
+static bool _GL_ATTRIBUTE_PURE
 contains_slash (const char *s)
 {
   for (; *s; s++)
diff --git a/src/util.h b/src/util.h
index 26a9a21..67f5e4d 100644
--- a/src/util.h
+++ b/src/util.h
@@ -74,7 +74,7 @@ enum file_attributes {
 void set_file_attributes (char const *, enum file_attributes, char const *,
 			  struct stat *, mode_t, struct timespec *);
 
-static inline char const *
+static inline char const * _GL_ATTRIBUTE_PURE
 skip_spaces (char const *str)
 {
   while (ISSPACE ((unsigned char) *str))