[tz] [PROPOSED 3/4] Scale back on function attribute use

[Paul Eggert]

This is mostly to simplify the code.  It also fixes
a difftime gotcha that does not affect TZDB proper.
* zdump.c (delta, xstrsize, xmalloc, my_snprintf):
* zic.c (emalloc, estrdup):
Remove function attributes, as GCC no longer generates a false
positive if these attributes are absent.  (In general GCC should
not need to warn about static functions lacking attributes.)
* private.h (ATTRIBUTE_UNSEQUENCED, ATTRIBUTE_CONST, ATTRIBUTE_MALLOC):
Remove; no longer used.
(difftime): ATTRIBUTE_PURE, not ATTRIBUTE_CONST, since its
observable behavior can depend on floating-point environment.
This change does not fix a tzcode bug, as tzcode never calls
difftime.  However, it could fix a bug elsewhere, if code is taken
from private.h and used elsewhere.
---
 private.h | 19 +++----------------
 zdump.c   |  8 ++++----
 zic.c     |  4 ++--
 3 files changed, 9 insertions(+), 22 deletions(-)

diff --git a/private.h b/private.h
index 9aec6fc2..cf2370c8 100644
--- a/private.h
+++ b/private.h
@@ -551,27 +551,14 @@ typedef unsigned long uintmax_t;
 # define ATTRIBUTE_REPRODUCIBLE /* empty */
 #endif
 
-#if HAVE___HAS_C_ATTRIBUTE
-# if __has_c_attribute(unsequenced)
-#  define ATTRIBUTE_UNSEQUENCED [[unsequenced]]
-# endif
-#endif
-#ifndef ATTRIBUTE_UNSEQUENCED
-# define ATTRIBUTE_UNSEQUENCED /* empty */
-#endif
-
-/* __attribute__((const)) is stricter than [[unsequenced]] and
+/* GCC attributes that are useful in tzcode.
    __attribute__((pure)) is stricter than [[reproducible]],
-   so the latter are adequate substitutes in non-GCC C23 platforms.  */
+   so the latter is an adequate substitute in non-GCC C23 platforms.  */
 #if __GNUC__ < 3
-# define ATTRIBUTE_CONST ATTRIBUTE_UNSEQUENCED
 # define ATTRIBUTE_FORMAT(spec) /* empty */
-# define ATTRIBUTE_MALLOC /* empty */
 # define ATTRIBUTE_PURE ATTRIBUTE_REPRODUCIBLE
 #else
-# define ATTRIBUTE_CONST __attribute__((const))
 # define ATTRIBUTE_FORMAT(spec) __attribute__((format spec))
-# define ATTRIBUTE_MALLOC __attribute__((malloc))
 # define ATTRIBUTE_PURE __attribute__((pure))
 #endif
 
@@ -706,7 +693,7 @@ DEPRECATED_IN_C23 char *ctime(time_t const *);
 char *asctime_r(struct tm const *restrict, char *restrict);
 char *ctime_r(time_t const *, char *);
 #endif
-ATTRIBUTE_CONST double difftime(time_t, time_t);
+ATTRIBUTE_PURE double difftime(time_t, time_t);
 size_t strftime(char *restrict, size_t, char const *restrict,
 		struct tm const *restrict);
 # if HAVE_STRFTIME_L
diff --git a/zdump.c b/zdump.c
index edc4d666..86aceb45 100644
--- a/zdump.c
+++ b/zdump.c
@@ -89,7 +89,7 @@ static bool	warned;
 static bool	errout;
 
 static char const *abbr(struct tm const *);
-ATTRIBUTE_PURE static intmax_t delta(struct tm *, struct tm *);
+static intmax_t delta(struct tm *, struct tm *);
 static void dumptime(struct tm const *);
 static time_t hunt(timezone_t, time_t, time_t, bool);
 static void show(timezone_t, char *, time_t, bool);
@@ -151,7 +151,7 @@ sumsize(ptrdiff_t a, ptrdiff_t b)
 /* Return the size of of the string STR, including its trailing NUL.
    Report an error and exit if this would exceed INDEX_MAX which means
    pointer subtraction wouldn't work.  */
-static ptrdiff_t
+ATTRIBUTE_PURE static ptrdiff_t
 xstrsize(char const *str)
 {
   size_t len = strlen(str);
@@ -162,7 +162,7 @@ xstrsize(char const *str)
 
 /* Return a pointer to a newly allocated buffer of size SIZE, exiting
    on failure.  SIZE should be positive.  */
-ATTRIBUTE_MALLOC static void *
+static void *
 xmalloc(ptrdiff_t size)
 {
   void *p = malloc(size);
@@ -932,7 +932,7 @@ showextrema(timezone_t tz, char *zone, time_t lo, struct tm *lotmp, time_t hi)
 # include <stdarg.h>
 
 /* A substitute for snprintf that is good enough for zdump.  */
-ATTRIBUTE_FORMAT((printf, 3, 4)) static int
+static int
 my_snprintf(char *s, size_t size, char const *format, ...)
 {
   int n;
diff --git a/zic.c b/zic.c
index 36739cb0..19a0b953 100644
--- a/zic.c
+++ b/zic.c
@@ -523,7 +523,7 @@ memcheck(void *ptr)
 	return ptr;
 }
 
-ATTRIBUTE_MALLOC static void *
+static void *
 emalloc(size_t size)
 {
   return memcheck(malloc(size));
@@ -535,7 +535,7 @@ erealloc(void *ptr, size_t size)
   return memcheck(realloc(ptr, size));
 }
 
-ATTRIBUTE_MALLOC static char *
+static char *
 estrdup(char const *str)
 {
   return memcheck(strdup(str));
-- 
2.43.0