build: accommodate -Werror=suggest-attribute=pure

Now that we're using the latest manywarnings module from gnulib,
accommodate gcc's -Werror=suggest-attribute=pure option by marking
suggested functions with gnulib-defined _GL_ATTRIBUTE_PURE.
* src/kwset.c (hasevery): Mark function with pure attribute.
(bmexec): Likewise.
* src/dfa.c (nsubtoks, istrstr, find_pred, dfamusts): Likewise.
* configure.ac: Disable (for lib/) options that seem not to be worth
the trouble: -Wunsuffixed-float-constants and -Wformat-nonliteral.

3 files changed, 8 insertions, 6 deletions

diff --git a/configure.ac b/configure.ac
index 0478d520..6c0f29d4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -164,6 +164,8 @@ if test "$gl_gcc_warnings" = yes; then
   #nw="$nw -Wmissing-prototypes"
   nw="$nw -Wold-style-definition"
   nw="$nw -Wcast-align"
+  nw="$nw -Wunsuffixed-float-constants"
+  gl_WARN_ADD([-Wno-format-nonliteral])
   gl_MANYWARN_COMPLEMENT([GNULIB_WARN_CFLAGS], [$WARN_CFLAGS], [$nw])
   AC_SUBST([GNULIB_WARN_CFLAGS])
 fi
diff --git a/src/dfa.c b/src/dfa.c
index 9e7c1368..3214f296 100644
--- a/src/dfa.c
+++ b/src/dfa.c
@@ -755,7 +755,7 @@ static const struct dfa_ctype prednames[] = {
   { NULL, NULL, false }
 };
 
-static const struct dfa_ctype *
+static const struct dfa_ctype * _GL_ATTRIBUTE_PURE
 find_pred (const char *str)
 {
   unsigned int i;
@@ -1679,7 +1679,7 @@ atom (void)
 }
 
 /* Return the number of tokens in the given subexpression. */
-static int
+static int _GL_ATTRIBUTE_PURE
 nsubtoks (int tindex)
 {
   int ntoks1;
@@ -3605,7 +3605,7 @@ icpyalloc (char const *string)
   return icatalloc (NULL, string);
 }
 
-static char *
+static char * _GL_ATTRIBUTE_PURE
 istrstr (char const *lookin, char const *lookfor)
 {
   char const *cp;
@@ -4017,7 +4017,7 @@ dfaalloc (void)
   return xmalloc (sizeof (struct dfa));
 }
 
-struct dfamust *
+struct dfamust * _GL_ATTRIBUTE_PURE
 dfamusts (struct dfa const *d)
 {
   return d->musts;
diff --git a/src/kwset.c b/src/kwset.c
index ba556bbc..124096c7 100644
--- a/src/kwset.c
+++ b/src/kwset.c
@@ -350,7 +350,7 @@ treedelta (struct tree const *tree,
 }
 
 /* Return true if A has every label in B. */
-static int
+static int _GL_ATTRIBUTE_PURE
 hasevery (struct tree const *a, struct tree const *b)
 {
   if (!b)
@@ -497,7 +497,7 @@ kwsprep (kwset_t kws)
 }
 
 /* Fast boyer-moore search. */
-static size_t
+static size_t _GL_ATTRIBUTE_PURE
 bmexec (kwset_t kws, char const *text, size_t size)
 {
   struct kwset const *kwset;