LibC: Fix regression in printf

printf did not write out anything for %d when the value was zero.

2 files changed, 9 insertions, 2 deletions

diff --git a/userland/libc/stdio/vfprintf.c b/userland/libc/stdio/vfprintf.c
index 2ba3e2c..d384c1d 100644
--- a/userland/libc/stdio/vfprintf.c
+++ b/userland/libc/stdio/vfprintf.c
@@ -28,8 +28,13 @@ int fprint_num(FILE *f, long long n, int base, char *char_set, int prefix,
     n *= -1;
   }
 
-  for (; n != 0 && i < 32; i++, n /= base)
-    str[i] = char_set[(n % base)];
+  if (0 == n) {
+    str[i] = char_set[0];
+    i++;
+  } else {
+    for (; n != 0 && i < 32; i++, n /= base)
+      str[i] = char_set[(n % base)];
+  }
 
   if (is_signed) {
     str[i] = '-';
diff --git a/userland/test/test.c b/userland/test/test.c
index 29aa34c..33361a5 100644
--- a/userland/test/test.c
+++ b/userland/test/test.c
@@ -588,6 +588,8 @@ void printf_test(void) {
     buf_n = sprintf(buf, "oct: %00o", 1);
     EXP("oct: 1");
 
+    buf_n = sprintf(buf, "int: %d", 0);
+    EXP("int: 0");
     buf_n = sprintf(buf, "int: %-2dend", 1);
     EXP("int: 1 end");
     buf_n = sprintf(buf, "int: %-2dend", 12);