[PATCH 5/7] maint: enable -Wsuggest-attribute=format

[Paul Eggert]

* configure.ac (WERROR_CFLAGS): Enable -Wsuggest-attribute=format
for lib/ and src/.
* src/copy.c (copy_attr_error, copy_attr_allerror):
Add ATTRIBUTE_FORMAT.
(copy_attr): Ignore -Wsuggest-attribute=format in the
small section of code that needs it ignored.
* src/test.c (test_syntax_error): Mark with ATTRIBUTE_FORMAT.
(binary_operator): Omit unnecessary NULL args, pacifying
-Wsuggest-attribute=format.
---
 configure.ac |  2 +-
 src/copy.c   | 44 ++++++++++++++++++++++++++------------------
 src/test.c   |  7 ++++---
 3 files changed, 31 insertions(+), 22 deletions(-)

diff --git a/configure.ac b/configure.ac
index 6960b486a..3f72068bf 100644
--- a/configure.ac
+++ b/configure.ac
@@ -150,7 +150,6 @@ if test $gl_gcc_warnings != no; then
   nw="$nw -Wmissing-format-attribute" # copy.c
   nw="$nw -Wunsafe-loop-optimizations" # a few src/*.c
   nw="$nw -Winline"                 # system.h's 
readdir_ignoring_dot_and_dotdot
-  nw="$nw -Wsuggest-attribute=format" # warns about copy.c and factor.c
   nw="$nw -Wvector-operation-performance" # warns about randperm.c
 
 
@@ -224,6 +223,7 @@ if test $gl_gcc_warnings != no; then
   nw="$nw -Wstrict-prototypes"
   # It's not worth being this picky about test programs.
   nw="$nw -Wsuggest-attribute=const"
+  nw="$nw -Wsuggest-attribute=format"
   nw="$nw -Wsuggest-attribute=pure"
   gl_MANYWARN_COMPLEMENT([GNULIB_TEST_WARN_CFLAGS],
                          [$GNULIB_WARN_CFLAGS], [$nw])
diff --git a/src/copy.c b/src/copy.c
index 8c69400ec..3704e129e 100644
--- a/src/copy.c
+++ b/src/copy.c
@@ -668,6 +668,7 @@ errno_unsupported (int err)
 }
 
 #if USE_XATTR
+ATTRIBUTE_FORMAT ((printf, 2, 3))
 static void
 copy_attr_error (struct error_context *ctx _GL_UNUSED,
                  char const *fmt, ...)
@@ -684,9 +685,10 @@ copy_attr_error (struct error_context *ctx _GL_UNUSED,
     }
 }
 
+ATTRIBUTE_FORMAT ((printf, 2, 3))
 static void
 copy_attr_allerror (struct error_context *ctx _GL_UNUSED,
-                 char const *fmt, ...)
+                    char const *fmt, ...)
 {
   int err = errno;
   va_list ap;
@@ -728,26 +730,32 @@ static bool
 copy_attr (char const *src_path, int src_fd,
            char const *dst_path, int dst_fd, struct cp_options const *x)
 {
-  int ret;
   bool all_errors = (!x->data_copy_required || x->require_preserve_xattr);
   bool some_errors = (!all_errors && !x->reduce_diagnostics);
-  bool selinux_done = (x->preserve_security_context || 
x->set_security_context);
-  struct error_context ctx =
-  {
-    .error = all_errors ? copy_attr_allerror : copy_attr_error,
-    .quote = copy_attr_quote,
-    .quote_free = copy_attr_free
-  };
-  if (0 <= src_fd && 0 <= dst_fd)
-    ret = attr_copy_fd (src_path, src_fd, dst_path, dst_fd,
-                        selinux_done ? check_selinux_attr : NULL,
-                        (all_errors || some_errors ? &ctx : NULL));
-  else
-    ret = attr_copy_file (src_path, dst_path,
-                          selinux_done ? check_selinux_attr : NULL,
-                          (all_errors || some_errors ? &ctx : NULL));
+  int (*check) (char const *, struct error_context *)
+    = (x->preserve_security_context || x->set_security_context
+       ? check_selinux_attr : NULL);
+
+# if 4 < __GNUC__ + (8 <= __GNUC_MINOR__)
+  /* Pacify gcc -Wsuggest-attribute=format through at least GCC 11.2.1.  */
+#  pragma GCC diagnostic push
+#  pragma GCC diagnostic ignored "-Wsuggest-attribute=format"
+# endif
+  struct error_context *ctx
+    = (all_errors || some_errors
+       ? (&(struct error_context) {
+           .error = all_errors ? copy_attr_allerror : copy_attr_error,
+           .quote = copy_attr_quote,
+           .quote_free = copy_attr_free
+         })
+       : NULL);
+# if 4 < __GNUC__ + (8 <= __GNUC_MINOR__)
+#  pragma GCC diagnostic pop
+# endif
 
-  return ret == 0;
+  return ! (0 <= src_fd && 0 <= dst_fd
+            ? attr_copy_fd (src_path, src_fd, dst_path, dst_fd, check, ctx)
+            : attr_copy_file (src_path, dst_path, check, ctx));
 }
 #else /* USE_XATTR */
 
diff --git a/src/test.c b/src/test.c
index 8f179ec02..79dc8d213 100644
--- a/src/test.c
+++ b/src/test.c
@@ -85,6 +85,7 @@ static bool or (void);
 
 static void beyond (void);
 
+ATTRIBUTE_FORMAT ((printf, 1, 2))
 static _Noreturn void
 test_syntax_error (char const *format, ...)
 {
@@ -323,7 +324,7 @@ binary_operator (bool l_is_l)
               bool le, re;
               pos += 3;
               if (l_is_l || r_is_l)
-                test_syntax_error (_("-nt does not accept -l"), NULL);
+                test_syntax_error (_("-nt does not accept -l"));
               le = get_mtime (argv[op - 1], &lt);
               re = get_mtime (argv[op + 1], &rt);
               return le && (!re || timespec_cmp (lt, rt) > 0);
@@ -336,7 +337,7 @@ binary_operator (bool l_is_l)
               /* ef - hard link? */
               pos += 3;
               if (l_is_l || r_is_l)
-                test_syntax_error (_("-ef does not accept -l"), NULL);
+                test_syntax_error (_("-ef does not accept -l"));
               return (stat (argv[op - 1], &stat_buf) == 0
                       && stat (argv[op + 1], &stat_spare) == 0
                       && stat_buf.st_dev == stat_spare.st_dev
@@ -352,7 +353,7 @@ binary_operator (bool l_is_l)
               bool le, re;
               pos += 3;
               if (l_is_l || r_is_l)
-                test_syntax_error (_("-ot does not accept -l"), NULL);
+                test_syntax_error (_("-ot does not accept -l"));
               le = get_mtime (argv[op - 1], &lt);
               re = get_mtime (argv[op + 1], &rt);
               return re && (!le || timespec_cmp (lt, rt) < 0);
-- 
2.31.1