Fixes eyalroz#63; (may) improve support for systems where the null po…

…inter representation is no all-0-bits.

* "splits" behavior of pointers and hash-marked base-16 values w.r.t the `0x` prefix (although you won't see the difference unless you un-special-case the handling of 0-valued pointer).
* Passing a null pointer for an `%s` now results in `(null)`.
* Added some relevant test suite assertions involving null/0 pointers as `%s` arguments.

printf.c

@@ -110,6 +110,8 @@
 #define FLAGS_LONG_LONG (1U <<  9U)
 #define FLAGS_PRECISION (1U << 10U)
 #define FLAGS_ADAPT_EXP (1U << 11U)
+#define FLAGS_POINTER   (1U << 12U)
+	// Note: Similar, but not identical, effect as FLAGS_HASH
 
 
 // import float.h for DBL_MAX
@@ -240,7 +242,7 @@ static size_t _ntoa_format(out_fct_type out, char* buffer, size_t idx, size_t ma
   }
 
   // handle hash
-  if (flags & FLAGS_HASH) {
+  if (flags & (FLAGS_HASH | FLAGS_POINTER)) {
     if (!(flags & FLAGS_PRECISION) && len && ((len == prec) || (len == width))) {
       len--;
       if (len && (base == 16U)) {
@@ -798,24 +800,29 @@ static int _vsnprintf(out_fct_type out, char* buffer, const size_t maxlen, const
 
       case 's' : {
         const char* p = va_arg(va, char*);
-        unsigned int l = _strnlen_s(p, precision ? precision : (size_t)-1);
-        // pre padding
-        if (flags & FLAGS_PRECISION) {
-          l = (l < precision ? l : precision);
-        }
-        if (!(flags & FLAGS_LEFT)) {
-          while (l++ < width) {
-            out(' ', buffer, idx++, maxlen);
+        if (p == NULL) {
+          idx = _out_rev(out, buffer, idx, maxlen, ")llun(", 6, width, flags);
+        } 
+		else {
+          unsigned int l = _strnlen_s(p, precision ? precision : (size_t)-1);
+          // pre padding
+          if (flags & FLAGS_PRECISION) {
+            l = (l < precision ? l : precision);
           }
-        }
-        // string output
-        while ((*p != 0) && (!(flags & FLAGS_PRECISION) || precision--)) {
-          out(*(p++), buffer, idx++, maxlen);
-        }
-        // post padding
-        if (flags & FLAGS_LEFT) {
-          while (l++ < width) {
-            out(' ', buffer, idx++, maxlen);
+          if (!(flags & FLAGS_LEFT)) {
+            while (l++ < width) {
+              out(' ', buffer, idx++, maxlen);
+            }
+          }
+          // string output
+          while ((*p != 0) && (!(flags & FLAGS_PRECISION) || precision--)) {
+            out(*(p++), buffer, idx++, maxlen);
+          }
+          // post padding
+          if (flags & FLAGS_LEFT) {
+            while (l++ < width) {
+              out(' ', buffer, idx++, maxlen);
+            }
           }
         }
         format++;
@@ -824,12 +831,13 @@ static int _vsnprintf(out_fct_type out, char* buffer, const size_t maxlen, const
 
       case 'p' : {
         width = sizeof(void*) * 2U + 2; // 2 hex chars per byte + the "0x" prefix
-        flags |= FLAGS_ZEROPAD | FLAGS_HASH;
+        flags |= FLAGS_ZEROPAD | FLAGS_POINTER;
         uintptr_t value = (uintptr_t)va_arg(va, void*);
 
-        if (value == 0) {
+        if (value == (uintptr_t) NULL) {
           idx = _out_rev(out, buffer, idx, maxlen, ")lin(", 5, width, flags);
-        } else {
+        } 
+		else {
 #if defined(PRINTF_SUPPORT_LONG_LONG)
           const bool is_ll = sizeof(uintptr_t) == sizeof(long long);
           if (is_ll) {

test/test_suite.cpp

@@ -263,9 +263,6 @@ TEST_CASE("space flag - non-standard format", "[]" ) {
   test::sprintf(buffer, "% s", "Hello testing");
   REQUIRE(!strcmp(buffer, "Hello testing"));
 
-  test::sprintf(buffer, "% s", "Hello testing");
-  REQUIRE(!strcmp(buffer, "Hello testing"));
-
   test::sprintf(buffer, "% u", 1024);
   REQUIRE(!strcmp(buffer, "1024"));
 
@@ -515,6 +512,9 @@ TEST_CASE("specifier", "[]" ) {
   test::sprintf(buffer, "%s", "Hello testing");
   REQUIRE(!strcmp(buffer, "Hello testing"));
 
+  test::sprintf(buffer, "%s", NULL);
+  REQUIRE(!strcmp(buffer, "(null)"));
+
   test::sprintf(buffer, "%d", 1024);
   REQUIRE(!strcmp(buffer, "1024"));
 
@@ -1506,7 +1506,7 @@ TEST_CASE("pointer", "[]" ) {
     REQUIRE(!strcmp(buffer, "0xffffffff"));
   }
 
-  test::sprintf(buffer, "%p", (void*) nullptr);
+  test::sprintf(buffer, "%p", NULL);
   REQUIRE(!strcmp(buffer, "(nil)"));
 }
 
@@ -1539,6 +1539,9 @@ TEST_CASE("string length", "[]" ) {
 
   test::sprintf(buffer, "%.*s", 3, "123456");
   REQUIRE(!strcmp(buffer, "123"));
+
+  test::sprintf(buffer, "%.*s", 3, NULL);
+  REQUIRE(!strcmp(buffer, "(null)"));
 }
 
 #ifdef TEST_WITH_NON_STANDARD_FORMAT_STRINGS
@@ -1571,6 +1574,9 @@ TEST_CASE("buffer length", "[]" ) {
 
   test::snprintf(buffer, 2, "%s", "Hello");
   REQUIRE(!strcmp(buffer, "H"));
+
+  test::snprintf(buffer, 2, "%s", NULL);
+  REQUIRE(!strcmp(buffer, "("));
 }
 
 
@@ -1584,11 +1590,15 @@ TEST_CASE("ret value", "[]" ) {
 
   ret = test::snprintf(buffer, 6, "0%s", "12345");
   REQUIRE(!strcmp(buffer, "01234"));
-  REQUIRE(ret == 6);  // '5' is truncated
+  REQUIRE(ret == 6);  // "5" is truncated
 
   ret = test::snprintf(buffer, 6, "0%s", "1234567");
   REQUIRE(!strcmp(buffer, "01234"));
-  REQUIRE(ret == 8);  // '567' are truncated
+  REQUIRE(ret == 8);  // "567" are truncated
+
+  ret = test::snprintf(buffer, 6, "0%s", NULL);
+  REQUIRE(!strcmp(buffer, "0(nul"));
+  REQUIRE(ret == 7);  // "l)" is truncated
 
   ret = test::snprintf(buffer, 10, "hello, world");
   REQUIRE(ret == 12);