+/**
+ * Print a formated message to a dynamically allocated string.
+ *
+ * \param result The formated string is returned here.
+ * \param fmt The format string.
+ * \param ap Initialized list of arguments.
+ *
+ * This function is similar to vasprintf(), a GNU extension which is not in C
+ * or POSIX. It allocates a string large enough to hold the output including
+ * the terminating null byte. The allocated string is returned via the first
+ * argument and must be freed by the caller. However, unlike vasprintf(), this
+ * function calls exit() if insufficient memory is available, while vasprintf()
+ * returns -1 in this case.
+ *
+ * \return Number of bytes written, not including the terminating \p NULL
+ * character.
+ *
+ * \sa printf(3), vsnprintf(3), va_start(3), vasprintf(3), \ref xasprintf().
+ */
+__printf_2_0 unsigned xvasprintf(char **result, const char *fmt, va_list ap)
+{
+ int ret;
+ size_t size;
+ va_list aq;
+
+ va_copy(aq, ap);
+ ret = vsnprintf(NULL, 0, fmt, aq);
+ va_end(aq);
+ assert(ret >= 0);
+ size = ret + 1;
+ *result = para_malloc(size);
+ va_copy(aq, ap);
+ ret = vsnprintf(*result, size, fmt, aq);
+ va_end(aq);
+ assert(ret >= 0 && ret < size);
+ return ret;
+}
+
+/**
+ * Print to a dynamically allocated string, variable number of arguments.
+ *
+ * \param result See \ref xvasprintf().
+ * \param fmt Usual format string.
+ *
+ * \return The return value of the underlying call to \ref xvasprintf().
+ *
+ * \sa \ref xvasprintf() and the references mentioned there.
+ */
+__printf_2_3 unsigned xasprintf(char **result, const char *fmt, ...)
+{
+ va_list ap;
+ unsigned ret;
+
+ va_start(ap, fmt);
+ ret = xvasprintf(result, fmt, ap);
+ va_end(ap);
+ return ret;
+}
+