stdio: add asprintf and vasprintf

CMakeLists.txt

@@ -114,6 +114,7 @@ set(SOURCES
   src/libc/signal/signal.c
   src/libc/signal/raise.c
   # stdio
+  src/libc/stdio/asprintf.c
   src/libc/stdio/dprintf.c
   src/libc/stdio/fprintf.c
   src/libc/stdio/printf.c
@@ -124,6 +125,7 @@ set(SOURCES
   src/libc/stdio/puts.c
   src/libc/stdio/snprintf.c
   src/libc/stdio/sprintf.c
+  src/libc/stdio/vasprintf.c
   src/libc/stdio/vdprintf.c
   src/libc/stdio/vfprintf.c
   src/libc/stdio/vprintf.c

include/stdio.h

@@ -81,4 +81,11 @@ extern int dprintf(int __fd, char const * restrict __format, ...);
 /* Formatted print to file descriptor (variable argument list). */
 extern int vdprintf(int __fd, char const * restrict __format, va_list __args);
 
+/* Allocating sprintf(). */
+extern int asprintf(char ** restrict __str,char const * restrict __format,...);
+
+/* Allocating vsprintf(). */
+extern int vasprintf(char ** restrict __str, char const * restrict __format,
+	va_list __args);
+
 #endif /*__STDIO_H__*/

src/libc/stdio/asprintf.c

@@ -0,0 +1,13 @@
+#include <stdio.h>
+
+int asprintf(char **strp, char const *format, ...)
+{
+	va_list args;
+	va_start(args, format);
+
+	int count = vasprintf(strp, format, args);
+
+	va_end(args);
+	return count;
+}
+

src/libc/stdio/vasprintf.c

@@ -0,0 +1,19 @@
+#include <stdio.h>
+#include <stdlib.h>
+
+int vasprintf(char **strp, char const *format, va_list args1)
+{
+	va_list args2;
+	va_copy(args2, args1);
+
+	int count = vsnprintf(NULL, 0, format, args1);
+	va_end(args1);
+
+	char *str = malloc(count + 1);
+	if(str) count = vsnprintf(str, count + 1, format, args2);
+	va_end(args2);
+
+	if(!str) return -1;
+	*strp = str;
+	return count;
+}