Prevent ## to appear at start or end of macro

tccpp.c

@@ -1213,9 +1213,9 @@ static void tok_print(int *str)
 ST_FUNC void parse_define(void)
 {
     Sym *s, *first, **ps;
-    int v, t, varg, is_vaargs, spc;
+    int v, t, varg, is_vaargs, spc, ptok, macro_list_start;
     TokenString str;
-    
+
     v = tok;
     if (v < TOK_IDENT)
         tcc_error("invalid macro name '%s'", get_tok_str(tok, &tokc));
@@ -1254,8 +1254,13 @@ ST_FUNC void parse_define(void)
     tok_str_new(&str);
     spc = 2;
     /* EOF testing necessary for '-D' handling */
+    ptok = 0;
+    macro_list_start = 1;
     while (tok != TOK_LINEFEED && tok != TOK_EOF) {
-        /* remove spaces around ## and after '#' */        
+        if (!macro_list_start && spc == 2 && tok == TOK_TWOSHARPS)
+            tcc_error("'##' invalid at start of macro");
+        ptok = tok;
+        /* remove spaces around ## and after '#' */
         if (TOK_TWOSHARPS == tok) {
             if (1 == spc)
                 --str.len;
@@ -1268,7 +1273,10 @@ ST_FUNC void parse_define(void)
         tok_str_add2(&str, tok, &tokc);
     skip:
         next_nomacro_spc();
+        macro_list_start = 0;
     }
+    if (ptok == TOK_TWOSHARPS)
+        tcc_error("'##' invalid at end of macro");
     if (spc == 1)
         --str.len; /* remove trailing space */
     tok_str_add(&str, 0);

tests/tests2/65_macro_concat_start.c

@@ -0,0 +1,2 @@
+#define paste(A,B) ##A B
+paste(x,y)

tests/tests2/65_macro_concat_start.expect

@@ -0,0 +1 @@
+65_macro_concat_start.c:1: error: '##' invalid at start of macro

tests/tests2/66_macro_concat_end.c

@@ -0,0 +1,2 @@
+#define paste(A,B) A B##
+paste(x,y)

tests/tests2/66_macro_concat_end.expect

@@ -0,0 +1 @@
+66_macro_concat_end.c:2: error: '##' invalid at end of macro

tests/tests2/Makefile

@@ -79,7 +79,9 @@ TESTS =	\
  61_undefined_enum.test \
  62_enumerator_redefinition.test \
  63_local_enumerator_redefinition.test \
- 64_macro_nesting.test
+ 64_macro_nesting.test \
+ 65_macro_concat_start.test \
+ 66_macro_concat_end.test
 
 # 30_hanoi.test -- seg fault in the code, gcc as well
 # 34_array_assignment.test -- array assignment is not in C standard