regex: use C99-style array arg syntax

This should help with some static checking.
Derived from a suggestion by Martin Sebor in:
https://sourceware.org/pipermail/libc-alpha/2021-August/130336.html
This also ports recent and relevant Glibc changes to Gnulib
and prepares to copy back.
* lib/cdefs.h (__ARG_NELTS): New macro.
* lib/regex.c: Ignore -Wvla for the whole file.
* lib/regex.h (_ARG_NELTS_, _Attr_access_): New macros.
Ignore -Wvla when declaring regexec.
* lib/regex.h (re_compile_pattern, re_search, re_search_2)
(re_match, re_match_2, regcomp, regerror):
Use _Attr_access_ where that could help static checking.
* lib/regexec.c (regexec, __compat_regexec, re_copy_regs)
(re_search_internal, proceed_next_node, push_fail_stack)
(pop_fail_stack, set_regs, update_regs):
Use __ARG_NELTS for each array parameter whose size is another arg,
but which might be null.

1 files changed, 45 insertions, 7 deletions

diff --git a/lib/regex.h b/lib/regex.h
index 8e4ef45578..540c323163 100644
--- a/lib/regex.h
+++ b/lib/regex.h
@@ -522,6 +522,32 @@ typedef struct
 
 /* Declarations for routines.  */
 
+#ifndef _ARG_NELTS_
+# ifdef __ARG_NELTS
+#  define _ARG_NELTS_(arg) __ARG_NELTS (arg)
+# elif (defined __STDC_VERSION__ && 199901L <= __STDC_VERSION__ \
+	&& !defined __STDC_NO_VLA__)
+#  define _ARG_NELTS_(n) n
+# else
+#  define _ARG_NELTS_(n)
+# endif
+#endif
+
+#if defined __GNUC__ && 4 < __GNUC__ + (6 <= __GNUC_MINOR__)
+# pragma GCC diagnostic push
+# pragma GCC diagnostic ignored "-Wvla"
+#endif
+
+#ifndef _Attr_access_
+# ifdef __attr_access
+#  define _Attr_access_(arg) __attr_access (arg)
+# elif defined __GNUC__ && 10 <= __GNUC__
+#  define _Attr_access_(x) __attribute__ ((__access__ x))
+# else
+#  define _Attr_access_(x)
+# endif
+#endif
+
 #ifdef __USE_GNU
 /* Sets the current default syntax to SYNTAX, and return the old syntax.
    You can also simply assign to the 're_syntax_options' variable.  */
@@ -536,7 +562,8 @@ extern reg_syntax_t re_set_syntax (reg_syntax_t __syntax);
    'regcomp', with a malloc'ed value, or set to NULL before calling
    'regfree'.  */
 extern const char *re_compile_pattern (const char *__pattern, size_t __length,
-				       struct re_pattern_buffer *__buffer);
+				       struct re_pattern_buffer *__buffer)
+    _Attr_access_ ((__read_only__, 1, 2));
 
 
 /* Compile a fastmap for the compiled pattern in BUFFER; used to
@@ -553,7 +580,8 @@ extern int re_compile_fastmap (struct re_pattern_buffer *__buffer);
 extern regoff_t re_search (struct re_pattern_buffer *__buffer,
 			   const char *__String, regoff_t __length,
 			   regoff_t __start, regoff_t __range,
-			   struct re_registers *__regs);
+			   struct re_registers *__regs)
+    _Attr_access_ ((__read_only__, 2, 3));
 
 
 /* Like 're_search', but search in the concatenation of STRING1 and
@@ -563,14 +591,17 @@ extern regoff_t re_search_2 (struct re_pattern_buffer *__buffer,
 			     const char *__string2, regoff_t __length2,
 			     regoff_t __start, regoff_t __range,
 			     struct re_registers *__regs,
-			     regoff_t __stop);
+			     regoff_t __stop)
+    _Attr_access_ ((__read_only__, 2, 3))
+    _Attr_access_ ((__read_only__, 4, 5));
 
 
 /* Like 're_search', but return how many characters in STRING the regexp
    in BUFFER matched, starting at position START.  */
 extern regoff_t re_match (struct re_pattern_buffer *__buffer,
 			  const char *__String, regoff_t __length,
-			  regoff_t __start, struct re_registers *__regs);
+			  regoff_t __start, struct re_registers *__regs)
+    _Attr_access_ ((__read_only__, 2, 3));
 
 
 /* Relates to 're_match' as 're_search_2' relates to 're_search'.  */
@@ -578,7 +609,9 @@ extern regoff_t re_match_2 (struct re_pattern_buffer *__buffer,
 			    const char *__string1, regoff_t __length1,
 			    const char *__string2, regoff_t __length2,
 			    regoff_t __start, struct re_registers *__regs,
-			    regoff_t __stop);
+			    regoff_t __stop)
+    _Attr_access_ ((__read_only__, 2, 3))
+    _Attr_access_ ((__read_only__, 4, 5));
 
 
 /* Set REGS to hold NUM_REGS registers, storing them in STARTS and
@@ -648,13 +681,18 @@ extern int regcomp (regex_t *_Restrict_ __preg,
 extern int regexec (const regex_t *_Restrict_ __preg,
 		    const char *_Restrict_ __String, size_t __nmatch,
 		    regmatch_t __pmatch[_Restrict_arr_],
-		    int __eflags);
+		    int __eflags)
+    _Attr_access_ ((__write_only__, 4, 3));
 
 extern size_t regerror (int __errcode, const regex_t *_Restrict_ __preg,
-			char *_Restrict_ __errbuf, size_t __errbuf_size);
+			char *_Restrict_ __errbuf, size_t __errbuf_size)
+    _Attr_access_ ((__write_only__, 3, 4));
 
 extern void regfree (regex_t *__preg);
 
+#if defined __GNUC__ && 4 < __GNUC__ + (6 <= __GNUC_MINOR__)
+# pragma GCC diagnostic pop
+#endif
 
 #ifdef __cplusplus
 }