fix(printf): zero precision and zero value hash problem

Fixes #26

Author: mpaland

printf.c

@@ -163,9 +163,9 @@ static size_t _ntoa_format(out_fct_type out, char* buffer, size_t idx, size_t ma
 
   // handle hash
   if (flags & FLAGS_HASH) {
-    if (((len == prec) || (len == width)) && (len > 0U)) {
+    if (len && ((len == prec) || (len == width))) {
       len--;
-      if ((base == 16U) && (len > 0U)) {
+      if (len && (base == 16U)) {
         len--;
       }
     }
@@ -181,7 +181,7 @@ static size_t _ntoa_format(out_fct_type out, char* buffer, size_t idx, size_t ma
   }
 
   // handle sign
-  if ((len == width) && (negative || (flags & FLAGS_PLUS) || (flags & FLAGS_SPACE))) {
+  if (len && (len == width) && (negative || (flags & FLAGS_PLUS) || (flags & FLAGS_SPACE))) {
     len--;
   }
   if (len < PRINTF_NTOA_BUFFER_SIZE) {
@@ -225,6 +225,11 @@ static size_t _ntoa_long(out_fct_type out, char* buffer, size_t idx, size_t maxl
   char buf[PRINTF_NTOA_BUFFER_SIZE];
   size_t len = 0U;
 
+  // no hash for 0 values
+  if (!value) {
+    flags &= ~FLAGS_HASH;
+  }
+
   // write if precision != 0 and value is != 0
   if (!(flags & FLAGS_PRECISION) || value) {
     do {
@@ -245,6 +250,11 @@ static size_t _ntoa_long_long(out_fct_type out, char* buffer, size_t idx, size_t
   char buf[PRINTF_NTOA_BUFFER_SIZE];
   size_t len = 0U;
 
+  // no hash for 0 values
+  if (!value) {
+    flags &= ~FLAGS_HASH;
+  }
+
   // write if precision != 0 and value is != 0
   if (!(flags & FLAGS_PRECISION) || value) {
     do {

test/test_suite.cpp

@@ -247,6 +247,9 @@ TEST_CASE("+ flag", "[]" ) {
 
   test::sprintf(buffer, "%+c", 'x');
   REQUIRE(!strcmp(buffer, "x"));
+
+  test::sprintf(buffer, "%+.0d", 0);
+  REQUIRE(!strcmp(buffer, "+"));
 }
 
 
@@ -344,6 +347,14 @@ TEST_CASE("- flag", "[]" ) {
 }
 
 
+TEST_CASE("# flag", "[]" ) {
+  char buffer[100];
+
+  test::sprintf(buffer, "%#.0x", 0);
+  REQUIRE(!strcmp(buffer, ""));
+}
+
+
 TEST_CASE("specifier", "[]" ) {
   char buffer[100];
 
@@ -1232,6 +1243,9 @@ TEST_CASE("misc", "[]" ) {
   test::sprintf(buffer, "%.3s", "foobar");
   REQUIRE(!strcmp(buffer, "foo"));
 
+  test::sprintf(buffer, "% .0d", 0);
+  REQUIRE(!strcmp(buffer, " "));
+
   test::sprintf(buffer, "%10.5d", 4);
   REQUIRE(!strcmp(buffer, "     00004"));