bug:

----------------------------------------------------------------------
#define hexCh(c (c >= 10 ? 'a' + c - 10 : '0' + c)
  hexCh(c);

out:
jiang@jiang:~/test$ ./tcc -E c4.c
# 1 "c4.c"

(c >= 10 ? 'a' + c - 10 : '0' + c);
---------------------------------------------------------------

#define hexCh(c/3) (c >= 10 ? 'a' + c - 10 : '0' + c)
hexCh(c);

out:
jiang@jiang:~/test$ ./tcc -E c4.c
# 1 "c4.c"

/3) (c >= 10 ? 'a' + c - 10 : '0' + c);
jiang@jiang:~/test$

after patch:

# 1 "c4.c"
c4.c:1: error: may not appear in macro parameter list: "("
jiang@jiang:~/test$

jiang@jiang:~/test$ ./tcc -E c4.c
# 1 "c4.c"
c4.c:1: error: may not appear in macro parameter list: "/"
jiang@jiang:~/test$

tests/tests2/68_macro_concat.c

@@ -0,0 +1,9 @@
+#include <stdio.h>
+#define hexCh(c (c >= 10 ? 'a' + c - 10 : '0' + c)
+
+int main(void)
+{
+    int c = 0xa; 
+    printf("hex: %c\n", hexCh(c));
+    return 0;
+}