* and #pragma pop_macro("macro_name")

* give warning if pragma is unknown for tcc
    * don't free asm_label in sym_free(),
      it's a job of the asm_free_labels().

    The above pragmas are used in the mingw headers.
    Thise pragmas are implemented in gcc-4.5+ and current
    clang.

tcc.h

@@ -326,6 +326,7 @@
 typedef struct TokenSym {
     struct TokenSym *hash_next;
     struct Sym *sym_define; /* direct pointer to define */
+    struct Sym *sym_define_stack; /* direct pointer to a push_macro stack */
     struct Sym *sym_label; /* direct pointer to label */
     struct Sym *sym_struct; /* direct pointer to structure */
     struct Sym *sym_identifier; /* direct pointer to identifier */

tccasm.c

@@ -292,7 +292,7 @@ static void asm_free_labels(TCCState *st)
 {
     Sym *s, *s1;
     Section *sec;
-    
+
     for(s = st->asm_labels; s != NULL; s = s1) {
         s1 = s->prev;
         /* define symbol value in object file */
@@ -305,6 +305,9 @@ static void asm_free_labels(TCCState *st)
         }
         /* remove label */
         table_ident[s->v - TOK_IDENT]->sym_label = NULL;
+        if (s->asm_label) {
+            tcc_free(s->asm_label);
+        }
         sym_free(s);
     }
     st->asm_labels = NULL;

tccgen.c

@@ -152,7 +152,6 @@ static inline Sym *sym_malloc(void)
 ST_INLN void sym_free(Sym *sym)
 {
     sym->next = sym_free_first;
-    tcc_free(sym->asm_label);
     sym_free_first = sym;
 }
 

tccpp.c

@@ -222,6 +222,7 @@ static TokenSym *tok_alloc_new(TokenSym **pts, const char *str, int len)
     table_ident[i] = ts;
     ts->tok = tok_ident++;
     ts->sym_define = NULL;
+    ts->sym_define_stack = NULL;
     ts->sym_label = NULL;
     ts->sym_struct = NULL;
     ts->sym_identifier = NULL;
@@ -1446,6 +1447,39 @@ static void pragma_parse(TCCState *s1)
         } else {
             tcc_warning("#pragma comment(lib) is ignored");
         }
+    } else if ((tok == TOK_push_macro) || (tok == TOK_pop_macro)) {
+            int push_macro = (tok == TOK_push_macro);
+            next();
+            skip('(');
+            if (tok != TOK_STR) {
+                expect("\"");
+            } else {
+                int len = strlen((char *)tokc.cstr->data);
+                tcc_open_bf(s1, "<push_pop_macro>", len);
+                memcpy(file->buffer, tokc.cstr->data, len);
+                ch = file->buf_ptr[0];
+                next_nomacro();
+                if (tok >= TOK_IDENT) {
+                    Sym *s = table_ident[tok - TOK_IDENT]->sym_define;
+                    Sym *ss = table_ident[tok - TOK_IDENT]->sym_define_stack;
+                    if (push_macro) {
+                        if (s) {
+                            s->prev_tok = ss;
+                            table_ident[tok - TOK_IDENT]->sym_define_stack = s;
+                        }
+                    } else {
+                        if (ss) {
+                            table_ident[tok - TOK_IDENT]->sym_define = ss;
+                            table_ident[tok - TOK_IDENT]->sym_define_stack = ss->prev_tok;
+                        }
+                    }
+                }
+                tcc_close();
+            }
+            next();
+            skip(')');
+    } else {
+        tcc_warning("unknown #pragma %s", get_tok_str(tok, &tokc));
     }
 }
 

tcctok.h

@@ -155,6 +155,8 @@
 #endif
      DEF(TOK_comment, "comment")
      DEF(TOK_lib, "lib")
+     DEF(TOK_push_macro, "push_macro")
+     DEF(TOK_pop_macro, "pop_macro")
 
 /* builtin functions or variables */
 #ifndef TCC_ARM_EABI

tests/tests2/77_push_pop_macro.c

@@ -0,0 +1,23 @@
+#include <stdio.h>
+
+int main()
+{
+    #define abort "111"
+    printf("abort = %s\n", abort);
+
+    #pragma push_macro("abort")
+    #undef abort
+    #define abort "222"
+    printf("abort = %s\n", abort);
+
+    #pragma push_macro("abort")
+    #undef abort
+    #define abort "333"
+    printf("abort = %s\n", abort);
+
+    #pragma pop_macro("abort")
+    printf("abort = %s\n", abort);
+
+    #pragma pop_macro("abort")
+    printf("abort = %s\n", abort);
+}

tests/tests2/77_push_pop_macro.expect

@@ -0,0 +1,5 @@
+abort = 111
+abort = 222
+abort = 333
+abort = 222
+abort = 111

tests/tests2/Makefile

@@ -95,7 +95,8 @@ TESTS =	\
  73_arm64.test \
  74_nocode_wanted.test \
  75_array_in_struct_init.test \
- 76_dollars_in_identifiers.test
+ 76_dollars_in_identifiers.test \
+ 77_push_pop_macro.test
 
 # 34_array_assignment.test -- array assignment is not in C standard