From 0f4b1600983f8afda41a02fec07424338785d81d Mon Sep 17 00:00:00 2001
From: pacien
Date: Tue, 5 Jun 2018 22:41:15 +0200
Subject: Prevent assigning to const

---
 src/generator.c    | 20 ++++++++++++++++++--
 src/generator.h    |  9 ++-------
 src/symbol_table.c | 20 ++++++++++++++++++++
 src/symbol_table.h |  8 ++++++++
 src/tpc.y          |  4 ++--
 5 files changed, 50 insertions(+), 11 deletions(-)

diff --git a/src/generator.c b/src/generator.c
index 3ecfe0d..f32f468 100644
--- a/src/generator.c
+++ b/src/generator.c
@@ -159,7 +159,12 @@ void gen_check(const char name[], Scope scope) {
 }
 
 // ----- READ AND PRINT FUNCTIONS -----
-void gen_reade(const char name[]) {
+void gen_reade(const char name[], Scope scope) {
+  if (is_read_only(name, scope)) {
+     fprintf(stderr, "Symbol \"%s\" at line %d is read only.\n", name, scope);
+     exit(1);
+  }
+
   if (loc_lookup(name) != INT) {
     fprintf(stderr, "Need to be a INT in the reade() function\n");
     return;
@@ -174,7 +179,12 @@ void gen_reade(const char name[]) {
   fprintf(output, "mov rax,globals\nadd rax,%d\ncall reade\n", g_addr);
 }
 
-void gen_readc(const char name[]) {
+void gen_readc(const char name[], Scope scope) {
+  if (is_read_only(name, scope)) {
+     fprintf(stderr, "Symbol \"%s\" at line %d is read only.\n", name, scope);
+     exit(1);
+  }
+
   if (loc_lookup(name) != CHAR) {
     fprintf(stderr, "Need to be a CHAR in the readc() function\n");
     return;
@@ -233,6 +243,12 @@ void gen_ifelse_end(int idx) {
 int gen_assign(const char ident[], Scope scope) {
   int l_addr = loc_get_addr(ident);
   int g_addr = glo_get_addr(ident);
+
+  if (is_read_only(ident, scope)) {
+     fprintf(stderr, "Symbol \"%s\" at line %d is read only.\n", ident, scope);
+     exit(1);
+  }
+
   switch (scope) {
   case GLOBAL:
     fprintf(output, "pop QWORD [globals + %d] ;%s\n", g_addr,
diff --git a/src/generator.h b/src/generator.h
index 6c132fd..d2ad5c2 100644
--- a/src/generator.h
+++ b/src/generator.h
@@ -10,11 +10,6 @@
 #include <stdbool.h>
 #include "symbol_table.h"
 
-typedef enum scope {
-  GLOBAL,
-  LOCAL
-} Scope;
-
 extern int nb_globals;
 extern int lineno;
 FILE *output;
@@ -32,8 +27,8 @@ Type gen_function_call(const char name[], int nb_param);
 void gen_declaration(const char name[], int type, Scope scope);
 void gen_check(const char name[], Scope scope);
 
-void gen_reade(const char name[]);
-void gen_readc(const char name[]);
+void gen_reade(const char name[], Scope scope);
+void gen_readc(const char name[], Scope scope);
 
 void gen_print(int type);
 
diff --git a/src/symbol_table.c b/src/symbol_table.c
index 08124ac..68e24f0 100644
--- a/src/symbol_table.c
+++ b/src/symbol_table.c
@@ -228,3 +228,23 @@ void check_expected_type(int type_to_check, int type_expected) {
             string_of_type(type_expected), string_of_type(type_to_check),
             lineno);
 }
+
+/* returns false if symbol can't be found too */
+bool is_read_only(const char name[], Scope scope) {
+  int count;
+
+  switch (scope) {
+  case LOCAL:
+    for (count = 0; count < loc_symbol_table.size; count++)
+      if (!strcmp(loc_symbol_table.entries[count].name, name))
+        return loc_symbol_table.entries[count].read_only;
+
+  case GLOBAL:
+    for (count = 0; count < glo_symbol_table.size; count++)
+      if (!strcmp(glo_symbol_table.entries[count].name, name))
+        return glo_symbol_table.entries[count].read_only;
+
+  default:
+    return false;
+  }
+}
diff --git a/src/symbol_table.h b/src/symbol_table.h
index b2c8879..23cd618 100644
--- a/src/symbol_table.h
+++ b/src/symbol_table.h
@@ -15,6 +15,11 @@
 #define MAXSYMBOLS 256
 #define MAXFUNCTIONS 256
 
+typedef enum scope {
+  GLOBAL,
+  LOCAL
+} Scope;
+
 typedef enum type {
   INT,
   CHAR,
@@ -54,12 +59,15 @@ void glo_addConst(const char name[]);
 int glo_lookup(const char name[]);
 int glo_get_addr(const char name[]);
 void glo_display_table();
+
 void loc_addVar(const char name[], int type);
 void loc_addConst(const char name[]);
 int loc_lookup(const char name[]);
 int loc_get_addr(const char name[]);
 void loc_display_table();
 void loc_clean_table();
+
 void check_expected_type(int type_to_check, int type_expected);
+bool is_read_only(const char name[], Scope scope);
 
 #endif
diff --git a/src/tpc.y b/src/tpc.y
index d8fd1f1..64652d9 100644
--- a/src/tpc.y
+++ b/src/tpc.y
@@ -121,8 +121,8 @@ Instr:
 | ';'
 | RETURN Exp ';'                 { gen_function_return(return_type, $<type>2); }
 | RETURN ';'                     { gen_function_return(return_type, VOID_T);}
-| READE '(' IDENT ')' ';'        { gen_reade($<ident>3); }
-| READC '(' IDENT ')' ';'        { gen_readc($<ident>3); }
+| READE '(' IDENT ')' ';'        { gen_reade($<ident>3, scope); }
+| READC '(' IDENT ')' ';'        { gen_readc($<ident>3, scope); }
 | PRINT '(' Exp ')' ';'          { gen_print($<type>3);}
 | IF '(' Exp IfHandling')' Instr { gen_if_label($<num>4); }
 | IF '(' Exp IfHandling')' Instr ELSE IfEndHandling Instr IfElseEndHandling
-- 
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