[PATCH 3/3] ISO C23: Port the code to ISO C23

From: Petr Písař <[email protected]>

With GCC 15, which defaults to ISO 23, a build failed, for example like
this:

    gcc -DLOCALEDIR=\"/usr/local/share/locale\" -DHAVE_CONFIG_H -I. -I..  -I../libopts -I. -I.. -I../lib -I
    ../lib -I../intl  -Wno-format-contains-nul -g -O2 -Wno-format-contains-nul -c -o shar.o shar.c
    In file included from local.h:23,
		     from shar-opts.h:354,
		     from shar.c:46:
    ../lib/system.h:78:7: error: conflicting types for ‘fdopen’; have ‘FILE *(void)’
       78 | FILE *fdopen ();
	  |       ^~~~~~

The cause is that ISO C23 changed a meaning of an empty argument list
from an unspecified list to no arguments.

Also K&R syntax is now deprecated and the compiler warned:

    encode.c: In function ‘write_encoded_bytes’:
    encode.c:33:1: warning: old-style function definition [-Wold-style-definition]
       33 | write_encoded_bytes (group, file)
	  | ^~~~~~~~~~~~~~~~~~~

This patch fixes both the erros and the warnigs by specifying all the
arguments in the modern syntax.

Signed-off-by: Petr Písař <[email protected]>
---
 lib/system.h   |  6 +++---
 src/encode.c   | 13 +++----------
 src/shar.c     |  2 +-
 src/uudecode.c |  2 +-
 4 files changed, 8 insertions(+), 15 deletions(-)

diff --git a/lib/system.h b/lib/system.h
index 2b9846b..811e8cf 100644
--- a/lib/system.h
+++ b/lib/system.h
@@ -52,7 +52,7 @@ typedef enum {false = 0, true = 1} bool;
 #endif
 
 #if !HAVE_DECL_STRTOIMAX && !defined strtoimax
-intmax_t strtoimax ();
+intmax_t strtoimax (const char *nptr, char **endptr, int base);
 #endif
 
 #if HAVE_STRING_H
@@ -75,8 +75,8 @@ intmax_t strtoimax ();
 # include <unistd.h>
 #endif
 
-FILE *fdopen ();
-FILE *popen ();
+FILE *fdopen (int fd, const char *mode);
+FILE *popen (const char *command, const char *type);
 
 /* Global functions of the shar package.  */
 
diff --git a/src/encode.c b/src/encode.c
index 09e0c69..b1de8bd 100644
--- a/src/encode.c
+++ b/src/encode.c
@@ -30,9 +30,7 @@
 `------------------------------------------*/
 
 static void
-write_encoded_bytes (group, file)
-     char *group;
-     FILE *file;
+write_encoded_bytes (char *group, FILE *file)
 {
   int c1, c2, c3, c4;
 
@@ -52,10 +50,7 @@ write_encoded_bytes (group, file)
 `--------------------------------------------------------------------*/
 
 static int
-read_raw_bytes (file, buffer, buffer_size)
-     FILE *file;
-     char *buffer;
-     int buffer_size;
+read_raw_bytes (FILE *file, char *buffer, int buffer_size)
 {
   int character;
   int counter;
@@ -75,9 +70,7 @@ read_raw_bytes (file, buffer, buffer_size)
 `----------------------------------------------------*/
 
 void
-copy_file_encoded (input, output)
-     FILE *input;
-     FILE *output;
+copy_file_encoded (FILE *input, FILE *output)
 {
   char buffer[LINE_BUFFER_SIZE];
   int counter;
diff --git a/src/shar.c b/src/shar.c
index 6d7ed1d..2c6e2e1 100644
--- a/src/shar.c
+++ b/src/shar.c
@@ -109,7 +109,7 @@ static inline unsigned char to_uchar (char ch) { return ch; }
 #define IS_GRAPH(_c) (isprint (to_uchar (_c)) && !isspace (to_uchar (_c)))
 #endif
 
-struct tm *localtime ();
+struct tm *localtime (const time_t *timep);
 
 #if MSDOS
           /* 1 extra for CR.  */
diff --git a/src/uudecode.c b/src/uudecode.c
index 0621c99..b8a316e 100644
--- a/src/uudecode.c
+++ b/src/uudecode.c
@@ -82,7 +82,7 @@ static char const cright_years_z[] =
 #define UU_CHMOD(_n, _fd, _m)   chmod ((_n), UU_MODE_BITS(_m))
 #endif
 
-struct passwd *getpwnam ();
+struct passwd *getpwnam (const char *name);
 
 static uudecode_exit_code_t read_stduu(
         const char *inname, const char *outname);
-- 
2.48.1