argmatch: use void* for raw memory pointers

[Akim Demaille]

This is certainly debatable.  It started when I meant to
update some piece of code that was using argmatch_to_argument
incorrectly.  But the signature of argmatch_to_argument was
really unsettling:

argmatch_to_argument (const void *value,
                      const char *const *arglist,
                      const char *vallist, size_t valsize)

vallist is a not a string, it's a pointer to the list of "values",
that can be anything, of size "valsize".  char* makes this harder
to understand in my opinion, void* makes more sense, even if that
means that in its implementation argmatch_to_argument needs to
cast to char* to perform pointer arithmetics.

WDYT?



commit 2168926d033188dac94559493399d9d877734f26
Author: Akim Demaille <address@hidden>
Date:   Thu Apr 18 22:23:02 2019 +0200

    argmatch: use void* for raw memory pointers
    
    * lib/argmatch.h, lib/argmatch.c (argmatch, argmatch_valid)
    (__xargmatch_internal, argmatch_to_argument): Use void* for pointers
    to "values", keep char* for strings.

diff --git a/ChangeLog b/ChangeLog
index 398c33968..7d6cb0b0a 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2019-04-18  Akim Demaille  <address@hidden>
+
+       argmatch: use void* for raw memory pointers
+       * lib/argmatch.h, lib/argmatch.c (argmatch, argmatch_valid)
+       (__xargmatch_internal, argmatch_to_argument): Use void* for pointers
+       to "values", keep char* for strings.
+
 2019-04-14  Paul Eggert  <address@hidden>
 
        * lib/str-two-way.h: Fix comment typo.
diff --git a/lib/argmatch.c b/lib/argmatch.c
index b9a3e400c..434708504 100644
--- a/lib/argmatch.c
+++ b/lib/argmatch.c
@@ -82,7 +82,7 @@ argmatch_exit_fn argmatch_die = __argmatch_die;
 
 ptrdiff_t
 argmatch (const char *arg, const char *const *arglist,
-          const char *vallist, size_t valsize)
+          const void *vallist, size_t valsize)
 {
   size_t i;                     /* Temporary index in ARGLIST.  */
   size_t arglen;                /* Length of ARG.  */
@@ -96,6 +96,8 @@ argmatch (const char *arg, const char *const *arglist,
     {
       if (!strncmp (arglist[i], arg, arglen))
         {
+          fprintf (stderr, "'%s'(%ld) vs. '%s'(%ld)\n",
+                   arglist[i], strlen (arglist[i]), arg, arglen);
           if (strlen (arglist[i]) == arglen)
             /* Exact match found.  */
             return i;
@@ -106,8 +108,8 @@ argmatch (const char *arg, const char *const *arglist,
             {
               /* Second nonexact match found.  */
               if (vallist == NULL
-                  || memcmp (vallist + valsize * matchind,
-                             vallist + valsize * i, valsize))
+                  || memcmp ((char const *) vallist + valsize * matchind,
+                             (char const *) vallist + valsize * i, valsize))
                 {
                   /* There is a real ambiguity, or we could not
                      disambiguate. */
@@ -144,7 +146,7 @@ argmatch_invalid (const char *context, const char *value, 
ptrdiff_t problem)
    VALSIZE is the size of the elements of VALLIST */
 void
 argmatch_valid (const char *const *arglist,
-                const char *vallist, size_t valsize)
+                const void *vallist, size_t valsize)
 {
   size_t i;
   const char *last_val = NULL;
@@ -154,10 +156,10 @@ argmatch_valid (const char *const *arglist,
   fputs (_("Valid arguments are:"), stderr);
   for (i = 0; arglist[i]; i++)
     if ((i == 0)
-        || memcmp (last_val, vallist + valsize * i, valsize))
+        || memcmp (last_val, (char const *) vallist + valsize * i, valsize))
       {
         fprintf (stderr, "\n  - %s", quote (arglist[i]));
-        last_val = vallist + valsize * i;
+        last_val = (char const *) vallist + valsize * i;
       }
     else
       {
@@ -175,7 +177,7 @@ argmatch_valid (const char *const *arglist,
 ptrdiff_t
 __xargmatch_internal (const char *context,
                       const char *arg, const char *const *arglist,
-                      const char *vallist, size_t valsize,
+                      const void *vallist, size_t valsize,
                       argmatch_exit_fn exit_fn)
 {
   ptrdiff_t res = argmatch (arg, arglist, vallist, valsize);
@@ -194,14 +196,14 @@ __xargmatch_internal (const char *context,
 /* Look for VALUE in VALLIST, an array of objects of size VALSIZE and
    return the first corresponding argument in ARGLIST */
 const char *
-argmatch_to_argument (const char *value,
+argmatch_to_argument (const void *value,
                       const char *const *arglist,
-                      const char *vallist, size_t valsize)
+                      const void *vallist, size_t valsize)
 {
   size_t i;
 
   for (i = 0; arglist[i]; i++)
-    if (!memcmp (value, vallist + valsize * i, valsize))
+    if (!memcmp (value, (char const *) vallist + valsize * i, valsize))
       return arglist[i];
   return NULL;
 }
diff --git a/lib/argmatch.h b/lib/argmatch.h
index 51d288587..50de57f29 100644
--- a/lib/argmatch.h
+++ b/lib/argmatch.h
@@ -44,10 +44,10 @@ extern "C" {
    to the same values in VALLIST).  */
 
 ptrdiff_t argmatch (char const *arg, char const *const *arglist,
-                    char const *vallist, size_t valsize) _GL_ATTRIBUTE_PURE;
+                    void const *vallist, size_t valsize) _GL_ATTRIBUTE_PURE;
 
 # define ARGMATCH(Arg, Arglist, Vallist) \
-  argmatch (Arg, Arglist, (char const *) (Vallist), sizeof *(Vallist))
+  argmatch (Arg, Arglist, (void const *) (Vallist), sizeof *(Vallist))
 
 /* xargmatch calls this function when it fails.  This function should not
    return.  By default, this is a function that calls ARGMATCH_DIE which
@@ -70,10 +70,10 @@ void argmatch_invalid (char const *context, char const 
*value,
 /* Report on stderr the list of possible arguments.  */
 
 void argmatch_valid (char const *const *arglist,
-                     char const *vallist, size_t valsize);
+                     void const *vallist, size_t valsize);
 
 # define ARGMATCH_VALID(Arglist, Vallist) \
-  argmatch_valid (Arglist, (char const *) (Vallist), sizeof *(Vallist))
+  argmatch_valid (Arglist, (void const *) (Vallist), sizeof *(Vallist))
 
 
 
@@ -82,27 +82,27 @@ void argmatch_valid (char const *const *arglist,
 
 ptrdiff_t __xargmatch_internal (char const *context,
                                 char const *arg, char const *const *arglist,
-                                char const *vallist, size_t valsize,
+                                void const *vallist, size_t valsize,
                                 argmatch_exit_fn exit_fn);
 
 /* Programmer friendly interface to __xargmatch_internal. */
 
 # define XARGMATCH(Context, Arg, Arglist, Vallist)              \
   ((Vallist) [__xargmatch_internal (Context, Arg, Arglist,      \
-                                    (char const *) (Vallist),   \
+                                    (void const *) (Vallist),   \
                                     sizeof *(Vallist),          \
                                     argmatch_die)])
 
 /* Convert a value into a corresponding argument. */
 
-char const *argmatch_to_argument (char const *value,
+char const *argmatch_to_argument (void const *value,
                                   char const *const *arglist,
-                                  char const *vallist, size_t valsize)
+                                  void const *vallist, size_t valsize)
   _GL_ATTRIBUTE_PURE;
 
 # define ARGMATCH_TO_ARGUMENT(Value, Arglist, Vallist)                  \
   argmatch_to_argument (Value, Arglist,                                 \
-                        (char const *) (Vallist), sizeof *(Vallist))
+                        (void const *) (Vallist), sizeof *(Vallist))
 
 #ifdef  __cplusplus
 }