From 3709f8de14187082b31647865922ee5fc6827018 Mon Sep 17 00:00:00 2001
From: Arthur Williams <taaparthur@gmail.com>
Date: Sun, 22 Nov 2020 00:02:09 -0600
Subject: [PATCH] Treat func pointers with different return types as not
 compatible

Tcc considered function ptrs with different return types to be
compatible which disallowed some otherwise valid operations like:
`_Generic(foo, int(*)():0, void(*)(void):1)`
which would fail to compile with a error message of "type match twice"

This changed also required longjump's return type to be void and
munmap's to be int to be compatible with standard headers.
---
 tccgen.c                       | 21 ++++++++++++---------
 tccpp.c                        |  4 ++--
 tests/tests2/94_generic.c      |  6 +++++-
 tests/tests2/94_generic.expect |  1 +
 4 files changed, 20 insertions(+), 12 deletions(-)

diff --git a/tccgen.c b/tccgen.c
index 26e9f53e..3b2201ca 100644
--- a/tccgen.c
+++ b/tccgen.c
@@ -80,7 +80,7 @@ ST_DATA int func_var; /* true if current function is variadic (used by return in
 ST_DATA int func_vc;
 static int last_line_num, new_file, func_ind; /* debug info control */
 ST_DATA const char *funcname;
-ST_DATA CType int_type, func_old_type, char_type, char_pointer_type;
+ST_DATA CType int_type, func_old_type, char_type, char_pointer_type, func_mem_move, void_type, void_ptr_type;
 static CString initstr;
 
 #if PTR_SIZE == 4
@@ -800,6 +800,14 @@ ST_FUNC void tccgen_init(TCCState *s1)
     char_pointer_type = char_type;
     mk_pointer(&char_pointer_type);
 
+    void_type.t = VT_VOID;
+    void_ptr_type = void_type;
+    mk_pointer(&void_ptr_type);
+    func_mem_move.t = VT_FUNC;
+    func_mem_move.ref = sym_push(SYM_FIELD, &void_ptr_type, 0, 0);
+    func_mem_move.ref->f.func_call = FUNC_CDECL;
+    func_mem_move.ref->f.func_type = FUNC_OLD;
+
     func_old_type.t = VT_FUNC;
     func_old_type.ref = sym_push(SYM_FIELD, &int_type, 0, 0);
     func_old_type.ref->f.func_call = FUNC_CDECL;
@@ -3029,16 +3037,11 @@ static int is_compatible_func(CType *type1, CType *type2)
         && s1->f.func_type != FUNC_OLD
         && s2->f.func_type != FUNC_OLD)
         return 0;
-    /* we should check the function return type for FUNC_OLD too
-       but that causes problems with the internally used support
-       functions such as TOK_memmove */
-    if (s1->f.func_type == FUNC_OLD && !s1->next)
-        return 1;
-    if (s2->f.func_type == FUNC_OLD && !s2->next)
-        return 1;
     for (;;) {
         if (!is_compatible_unqualified_types(&s1->type, &s2->type))
             return 0;
+        if (s1->f.func_type == FUNC_OLD || s2->f.func_type == FUNC_OLD )
+            return 1;
         s1 = s1->next;
         s2 = s2->next;
         if (!s1)
@@ -3907,7 +3910,7 @@ ST_FUNC void vstore(void)
             else
 #endif
             /* Use memmove, rather than memcpy, as dest and src may be same: */
-            vpush_global_sym(&func_old_type, TOK_memmove);
+            vpush_global_sym(&func_mem_move, TOK_memmove);
 
             vswap();
             /* source */
diff --git a/tccpp.c b/tccpp.c
index 2c0dab94..992019fa 100644
--- a/tccpp.c
+++ b/tccpp.c
@@ -3721,10 +3721,10 @@ static void tcc_predefs(CString *cstr)
     "__BOUND(void*,__aeabi_memset,(void*,int,__SIZE_TYPE__))\n"
 #endif
     "__BUILTIN(void,abort,(void))\n"
-    "__BOUND(int,longjmp,())\n"
+    "__BOUND(void,longjmp,())\n"
 #ifndef TCC_TARGET_PE
     "__BOUND(void*,mmap,())\n"
-    "__BOUND(void*,munmap,())\n"
+    "__BOUND(int,munmap,())\n"
 #endif
     "#undef __BUILTINBC\n"
     "#undef __BUILTIN\n"
diff --git a/tests/tests2/94_generic.c b/tests/tests2/94_generic.c
index 6e85c025..4a68bcdd 100644
--- a/tests/tests2/94_generic.c
+++ b/tests/tests2/94_generic.c
@@ -21,10 +21,12 @@ int b_f()
 }
 
 typedef int (*fptr)(int);
+typedef void (*vfptr)(int);
 int foo(int i)
 {
   return i;
 }
+void void_foo(int i) {}
 
 typedef int int_type1;
 
@@ -66,7 +68,9 @@ int main()
 				long long: "long long"));
 	i = _Generic(l, long: 1, int: 2);
 	printf("%d\n", i);
-	i = _Generic(foo, fptr: 3, int: 4);
+	i = _Generic(foo, fptr: 3, int: 4, vfptr: 5);
+	printf("%d\n", i);
+	i = _Generic(void_foo, fptr: 3, int: 4, vfptr: 5);
 	printf("%d\n", i);
 
 	(void)_Generic((int(*)[2]){0}, int(*)[2]:0, int(*)[4]:0); //shouldn't match twice
diff --git a/tests/tests2/94_generic.expect b/tests/tests2/94_generic.expect
index 748d78fa..80d4ed9b 100644
--- a/tests/tests2/94_generic.expect
+++ b/tests/tests2/94_generic.expect
@@ -12,3 +12,4 @@
 long
 1
 3
+5