provide asprintf functionality for internal use

I plan to use asprintf in some gssapi error-message management
routines, so let's make sure we have the functionality available,
implementing it locally if necessary.

This implementation assumes vsnprintf is available, an assumption that
the support library is already making at the moment.

Since this implementation requires calling vsnprintf potentially
multiple times with the same va_list, use va_copy if it's available,
or provide a hack version (which should work okay if va_list is a
scalar or array type that requires no other special handling, and if
va_end does nothing interesting, which is usually the case) if the
compiler doesn't provide it.

I also changed a couple bits of code to use asprintf, to make sure we
exercise our implementation in testing.

(C99 requires vsnprintf and va_copy; vasprintf is a GNU/BSD extension,
but an oh so useful one....)


* configure.in: Check for va_copy, or if va_list objects can be simply
assigned.  Define HAS_VA_COPY and CAN_COPY_VA_LIST as appropriate.
* include/k5-platform.h: Define a va_copy macro if the compiler
doesn't provide it.

* include/k5-platform.h: If vsnprintf isn't available from the OS,
abort compilation.  If vasprintf isn't available from the OS, provide
k5_{v,}asprintf based on vsnprintf and define {v,}asprintf macros.
* lib/krb5/keytab/t_keytab.c (do_test): Use asprintf.
* util/support/errors.c (krb5int_vset_error): Use asprintf
unconditionally.

ticket: new

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@19595 dc483132-0cff-0310-8789-dd5450dbe970

1 files changed, 92 insertions, 3 deletions

diff --git a/src/include/k5-platform.h b/src/include/k5-platform.h
index 757b122b3d..6cf4465066 100644
--- a/src/include/k5-platform.h
+++ b/src/include/k5-platform.h
@@ -1,7 +1,7 @@
 /*
  * k5-platform.h
  *
- * Copyright 2003, 2004, 2005 Massachusetts Institute of Technology.
+ * Copyright 2003, 2004, 2005, 2007 Massachusetts Institute of Technology.
  * All Rights Reserved.
  *
  * Export of this software from the United States of America may
@@ -33,14 +33,19 @@
  * + SIZE_MAX
  * + shared library init/fini hooks
  * + consistent getpwnam/getpwuid interfaces
+ * + va_copy fudged if not provided
+ * + [v]asprintf
  */
 
 #ifndef K5_PLATFORM_H
 #define K5_PLATFORM_H
 
 #include "autoconf.h"
-/* for memcpy */
 #include <string.h>
+#include <stdarg.h>
+#include <limits.h>
+#include <stdlib.h>
+#include <stdio.h>
 
 /* Initialization and finalization function support for libraries.
 
@@ -403,7 +408,6 @@ typedef struct { int error; unsigned char did_run; } k5_init_t;
 # define UINT64_TYPE unsigned long long
 #endif
 
-#include <limits.h>
 #ifndef SIZE_MAX
 # define SIZE_MAX ((size_t)((size_t)0 - 1))
 #endif
@@ -743,5 +747,90 @@ load_64_n (const unsigned char *p)
 	(*(OUT) = getpwuid(UID), *(OUT) == NULL ? -1 : 0)
 #endif
 
+/* Since the original ANSI C spec left it undefined whether or
+   how you could copy around a va_list, C 99 added va_copy.
+   For old implementations, let's do our best to fake it.
+
+   XXX Doesn't yet handle implementations with __va_copy (early draft)
+   or GCC's __builtin_va_copy.  */
+#if defined(HAS_VA_COPY) || defined(va_copy)
+/* Do nothing.  */
+#elif defined(CAN_COPY_VA_LIST)
+#define va_copy(dest, src)	((dest) = (src))
+#else
+/* Assume array type, but still simply copyable.
+
+   There is, theoretically, the possibility that va_start will
+   allocate some storage pointed to by the va_list, and in that case
+   we'll just lose.  If anyone cares, we could try to devise a test
+   for that case.  */
+#define va_copy(dest, src)	memcmp(dest, src, sizeof(va_list))
+#endif
+
+/* Provide [v]asprintf interfaces.  */
+#ifndef HAVE_VSNPRINTF
+#error We need an implementation of vsnprintf.
+#endif
+#ifndef HAVE_VASPRINTF
+#define vasprintf k5_vasprintf
+/* On error: BSD: Set *ret to NULL.  GNU: *ret is undefined.
+
+   Since we want to be able to use the GNU version directly, we need
+   provide only the weaker guarantee in this version.  */
+static inline int
+vasprintf(char **ret, const char *format, va_list ap)
+{
+    va_list ap2;
+    char *str = NULL, *nstr;
+    int len = 80, len2;
+
+    while (1) {
+	if (len < 0 || (size_t) len != len) {
+	    free(str);
+	    return -1;
+	}
+	nstr = realloc(str, (size_t) len);
+	if (nstr == NULL) {
+	    free(str);
+	    return -1;
+	}
+	str = nstr;
+	va_copy(ap2, ap);
+	len2 = vsnprintf(str, (size_t) len, format, ap2);
+	va_end(ap2);
+	if (len2 >= 0 && len2 < len) {
+	    if (len2 < len-1) {
+		/* In a lot of cases, 80 will be quite a lot more than
+		   we need.  */
+		nstr = realloc(str, (size_t) len2+1);
+		if (nstr)
+		    str = nstr;
+	    }
+	    *ret = str;
+	    return len2;
+	}
+	/* ISO C vsnprintf returns the needed length.  Some old
+	   vsnprintf implementations return -1 on truncation.  */
+	if (len2 >= len)
+	    len = len2 + 1;
+	else
+	    len *= 2;
+    }
+}
+/* Assume HAVE_ASPRINTF iff HAVE_VASPRINTF.  */
+#define asprintf k5_asprintf
+static inline int
+k5_asprintf(char **ret, const char *format, ...)
+{
+    va_list ap;
+    int n;
+
+    va_start(ap, format);
+    n = vasprintf(ret, format, ap);
+    va_end(ap);
+    return n;
+}
+#endif
+
 
 #endif /* K5_PLATFORM_H */