fix(printf): fix trailing field width in itoa conversion

Fixes #21

Author: mpaland

printf.c

@@ -151,6 +151,8 @@ static inline unsigned int _atoi(const char** str)
 // internal itoa format
 static size_t _ntoa_format(out_fct_type out, char* buffer, size_t idx, size_t maxlen, char* buf, size_t len, bool negative, unsigned int base, unsigned int prec, unsigned int width, unsigned int flags)
 {
+  const size_t start_idx = idx;
+
   // pad leading zeros
   while (!(flags & FLAGS_LEFT) && (len < prec) && (len < PRINTF_NTOA_BUFFER_SIZE)) {
     buf[len++] = '0';
@@ -208,7 +210,7 @@ static size_t _ntoa_format(out_fct_type out, char* buffer, size_t idx, size_t ma
 
   // append pad spaces up to given width
   if (flags & FLAGS_LEFT) {
-    while (idx < width) {
+    while (idx - start_idx < width) {
       out(' ', buffer, idx++, maxlen);
     }
   }

test/test_suite.cpp

@@ -582,6 +582,18 @@ TEST_CASE("width -20", "[]" ) {
 
   test::sprintf(buffer, "%-20c", 'x');
   REQUIRE(!strcmp(buffer, "x                   "));
+
+  test::sprintf(buffer, "|%5d| |%-2d| |%5d|", 9, 9, 9);
+  REQUIRE(!strcmp(buffer, "|    9| |9 | |    9|"));
+
+  test::sprintf(buffer, "|%5d| |%-2d| |%5d|", 10, 10, 10);
+  REQUIRE(!strcmp(buffer, "|   10| |10| |   10|"));
+
+  test::sprintf(buffer, "|%5d| |%-12d| |%5d|", 9, 9, 9);
+  REQUIRE(!strcmp(buffer, "|    9| |9           | |    9|"));
+
+  test::sprintf(buffer, "|%5d| |%-12d| |%5d|", 10, 10, 10);
+  REQUIRE(!strcmp(buffer, "|   10| |10          | |   10|"));
 }