Re: C++ support (2)

[Paul Eggert]

Bruno Haible <address@hidden> writes:

>       * lib/xalloc.h (xrealloc, xnrealloc, x2realloc, x2nrealloc, xmemdup)
>       [C++]: Add function template that provides result type propagation.

I guess something like that is OK, though I prefer to put it into
a C++ ghetto area of the code.

As for quotearg.c, I realize it's sometimes a win to support C++, but
sometimes it's otherwise, and it's not clear to me that it's worth the
hassle here.  It is a borderline case, though, so I suppose we can try
it.  Looking at the code, I think there are better ways to address the
problem, so I installed this patch instead.

2006-10-31  Paul Eggert  <address@hidden>

        Avoid some C++ diagnostics reported by Bruno Haible.
        * lib/quotearg.c (clone_quoting_options): Use xmemdup rather than
        xmalloc.
        (quotearg_alloc): Use xcharalloc rather than xmalloc.
        (struct slotvec): Move to top level.
        (quotearg_n_options): Rewrite to avoid xmalloc.
        * lib/xalloc.h (xcharalloc): New function.
        * (xrealloc, xnrealloc, x2realloc, x2nrealloc, xmemdup):
        [defined __cplusplus]: Add function template that provides result
        type propagation.  This part of the change is from Bruno Haible.

Index: lib/quotearg.c
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/quotearg.c,v
retrieving revision 1.50
diff -p -u -r1.50 quotearg.c
--- lib/quotearg.c      3 Oct 2006 06:33:39 -0000       1.50
+++ lib/quotearg.c      31 Oct 2006 21:50:00 -0000
@@ -122,8 +122,8 @@ struct quoting_options *
 clone_quoting_options (struct quoting_options *o)
 {
   int e = errno;
-  struct quoting_options *p = xmalloc (sizeof *p);
-  *p = *(o ? o : &default_quoting_options);
+  struct quoting_options *p = xmemdup (o ? o : &default_quoting_options,
+                                      sizeof *o);
   errno = e;
   return p;
 }
@@ -554,12 +554,19 @@ quotearg_alloc (char const *arg, size_t 
 {
   int e = errno;
   size_t bufsize = quotearg_buffer (0, 0, arg, argsize, o) + 1;
-  char *buf = xmalloc (bufsize);
+  char *buf = xcharalloc (bufsize);
   quotearg_buffer (buf, bufsize, arg, argsize, o);
   errno = e;
   return buf;
 }
 
+/* A storage slot with size and pointer to a value.  */
+struct slotvec
+{
+  size_t size;
+  char *val;
+};
+
 /* Use storage slot N to return a quoted version of argument ARG.
    ARG is of size ARGSIZE, but if that is SIZE_MAX, ARG is a
    null-terminated string.
@@ -579,13 +586,9 @@ quotearg_n_options (int n, char const *a
   static char slot0[256];
   static unsigned int nslots = 1;
   unsigned int n0 = n;
-  struct slotvec
-    {
-      size_t size;
-      char *val;
-    };
   static struct slotvec slotvec0 = {sizeof slot0, slot0};
   static struct slotvec *slotvec = &slotvec0;
+  struct slotvec *sv = slotvec;
 
   if (n < 0)
     abort ();
@@ -598,31 +601,29 @@ quotearg_n_options (int n, char const *a
         revert to the original type, so that the test in xalloc_oversized
         is once again performed only at compile time.  */
       size_t n1 = n0 + 1;
+      bool preallocated = (sv == &slotvec0);
 
-      if (xalloc_oversized (n1, sizeof *slotvec))
+      if (xalloc_oversized (n1, sizeof *sv))
        xalloc_die ();
 
-      if (slotvec == &slotvec0)
-       {
-         slotvec = xmalloc (sizeof *slotvec);
-         *slotvec = slotvec0;
-       }
-      slotvec = xrealloc (slotvec, n1 * sizeof *slotvec);
-      memset (slotvec + nslots, 0, (n1 - nslots) * sizeof *slotvec);
+      slotvec = sv = xrealloc (preallocated ? NULL : sv, n1 * sizeof *sv);
+      if (preallocated)
+       *sv = slotvec0;
+      memset (sv + nslots, 0, (n1 - nslots) * sizeof *sv);
       nslots = n1;
     }
 
   {
-    size_t size = slotvec[n].size;
-    char *val = slotvec[n].val;
+    size_t size = sv[n].size;
+    char *val = sv[n].val;
     size_t qsize = quotearg_buffer (val, size, arg, argsize, options);
 
     if (size <= qsize)
       {
-       slotvec[n].size = size = qsize + 1;
+       sv[n].size = size = qsize + 1;
        if (val != slot0)
          free (val);
-       slotvec[n].val = val = xmalloc (size);
+       sv[n].val = val = xcharalloc (size);
        quotearg_buffer (val, size, arg, argsize, options);
       }
 
Index: lib/xalloc.h
===================================================================
RCS file: /cvsroot/gnulib/gnulib/lib/xalloc.h,v
retrieving revision 1.28
diff -p -u -r1.28 xalloc.h
--- lib/xalloc.h        14 May 2005 06:03:58 -0000      1.28
+++ lib/xalloc.h        31 Oct 2006 21:50:01 -0000
@@ -71,8 +71,51 @@ char *xstrdup (char const *str);
 # define xalloc_oversized(n, s) \
     ((size_t) (sizeof (ptrdiff_t) <= sizeof (size_t) ? -1 : -2) / (s) < (n))
 
+/* Return a pointer to a new buffer of S bytes.  This is like xmalloc,
+   except it returns char *.  */
+static inline char *
+xcharalloc (size_t s)
+{
+  return (char *) xmalloc (s);
+}
+
 # ifdef __cplusplus
 }
+
+/* C++ does not allow conversions from void * to other pointer types
+   without a cast.  Use templates to work around the problem when
+   possible.  */
+
+template <typename T> inline T *
+xrealloc (T *p, size_t s)
+{
+  return (T *) xrealloc ((void *) p, s);
+}
+
+template <typename T> inline T *
+xnrealloc (T *p, size_t n, size_t s)
+{
+  return (T *) xnrealloc ((void *) p, n, s);
+}
+
+template <typename T> inline T *
+x2realloc (T *p, size_t *pn)
+{
+  return (T *) x2realloc ((void *) p, pn);
+}
+
+template <typename T> inline T *
+x2nrealloc (T *p, size_t *pn, size_t s)
+{
+  return (T *) x2nrealloc ((void *) p, pn, s);
+}
+
+template <typename T> inline T *
+xmemdup (T const *p, size_t s)
+{
+  return (T *) xmemdup ((void const *) p, s);
+}
+
 # endif