lib/libc: Update formatting for printf

 - indirect width specification via %*s of %*d or alike was not supported
 - Passing (NULL, 0, ...) to snprintf to know formatted string length
   was not supported

These are necessary for running kernel Benchmarks

Bug: None
Change-Id: I3722847d33e8f51adbe474354340341fdfba5877

1 files changed, 18 insertions, 4 deletions

diff --git a/lib/libc/printf.c b/lib/libc/printf.c
index 9723196e..a8b18ea5 100644
--- a/lib/libc/printf.c
+++ b/lib/libc/printf.c
@@ -26,6 +26,7 @@
 #include <stdarg.h>
 #include <sys/types.h>
 #include <stdio.h>
+#include <stdlib.h>
 #include <string.h>
 
 #ifdef UTEST_BUILD
@@ -114,10 +115,13 @@ int vsnprintf(char *str, size_t len, const char *fmt, va_list ap)
     args.pos = 0;
 
     wlen = _printf_unfiltered_engine(&_vsnprintf_output, (void *)&args, fmt, ap);
-    if (args.pos >= len)
-        str[len-1] = '\0';
-    else
-        str[wlen] = '\0';
+    if(len > 0) {
+        if (args.pos >= len)
+            str[len-1] = '\0';
+        else
+            str[wlen] = '\0';
+    }
+
     return wlen;
 }
 
@@ -564,6 +568,16 @@ next_format:
                 uc = va_arg(ap, unsigned int);
                 OUTPUT_CHAR(uc);
                 break;
+            case '*':
+            {
+                /* indirect format */
+                int f = va_arg(ap, int);
+                format_num = (unsigned int) abs(f);
+                if(f < 0) {
+                    flags |= LEFTFORMATFLAG;
+                }
+                goto next_format;
+            }
             case 's':
                 s = va_arg(ap, const char *);
                 if (s == 0)