fixes #2675

Cython/Utility/Buffer.c

@@ -298,6 +298,7 @@ static void __Pyx_BufFmt_RaiseUnexpectedChar(char ch) {
 
 static const char* __Pyx_BufFmt_DescribeTypeChar(char ch, int is_complex) {
   switch (ch) {
+    case '?': return "'bool'";
     case 'c': return "'char'";
     case 'b': return "'signed char'";
     case 'B': return "'unsigned char'";
@@ -342,7 +343,7 @@ static size_t __Pyx_BufFmt_TypeCharToStandardSize(char ch, int is_complex) {
 
 static size_t __Pyx_BufFmt_TypeCharToNativeSize(char ch, int is_complex) {
   switch (ch) {
-    case 'c': case 'b': case 'B': case 's': case 'p': return 1;
+    case '?': case 'c': case 'b': case 'B': case 's': case 'p': return 1;
     case 'h': case 'H': return sizeof(short);
     case 'i': case 'I': return sizeof(int);
     case 'l': case 'L': return sizeof(long);
@@ -431,7 +432,7 @@ static char __Pyx_BufFmt_TypeCharToGroup(char ch, int is_complex) {
     case 'b': case 'h': case 'i':
     case 'l': case 'q': case 's': case 'p':
         return 'I';
-    case 'B': case 'H': case 'I': case 'L': case 'Q':
+    case '?': case 'B': case 'H': case 'I': case 'L': case 'Q':
         return 'U';
     case 'f': case 'd': case 'g':
         return (is_complex ? 'C' : 'R');
@@ -752,7 +753,7 @@ static const char* __Pyx_BufFmt_CheckString(__Pyx_BufFmt_Context* ctx, const cha
           return NULL;
         }
         CYTHON_FALLTHROUGH;
-      case 'c': case 'b': case 'B': case 'h': case 'H': case 'i': case 'I':
+      case '?': case 'c': case 'b': case 'B': case 'h': case 'H': case 'i': case 'I':
       case 'l': case 'L': case 'q': case 'Q':
       case 'f': case 'd': case 'g':
       case 'O': case 'p':