Add caching of conditional directive chains (#468)

Author: glankk

simplecpp.cpp

@@ -3532,6 +3532,7 @@ void simplecpp::preprocess(simplecpp::TokenList &output, const simplecpp::TokenL
     // AlwaysFalse => drop all code in #if and #else
     enum IfState { True, ElseIsTrue, AlwaysFalse };
     std::stack<int> ifstates;
+    std::stack<const Token *> iftokens;
     ifstates.push(True);
 
     std::stack<const Token *> includetokenstack;
@@ -3855,15 +3856,24 @@ void simplecpp::preprocess(simplecpp::TokenList &output, const simplecpp::TokenL
                         ifstates.push(AlwaysFalse);
                     else
                         ifstates.push(conditionIsTrue ? True : ElseIsTrue);
+                    iftokens.push(rawtok);
                 } else if (ifstates.top() == True) {
                     ifstates.top() = AlwaysFalse;
+                    iftokens.top()->nextcond = rawtok;
+                    iftokens.top() = rawtok;
                 } else if (ifstates.top() == ElseIsTrue && conditionIsTrue) {
                     ifstates.top() = True;
+                    iftokens.top()->nextcond = rawtok;
+                    iftokens.top() = rawtok;
                 }
             } else if (rawtok->str() == ELSE) {
                 ifstates.top() = (ifstates.top() == ElseIsTrue) ? True : AlwaysFalse;
+                iftokens.top()->nextcond = rawtok;
+                iftokens.top() = rawtok;
             } else if (rawtok->str() == ENDIF) {
                 ifstates.pop();
+                iftokens.top()->nextcond = rawtok;
+                iftokens.pop();
             } else if (rawtok->str() == UNDEF) {
                 if (ifstates.top() == True) {
                     const Token *tok = rawtok->next;
@@ -3875,7 +3885,10 @@ void simplecpp::preprocess(simplecpp::TokenList &output, const simplecpp::TokenL
             } else if (ifstates.top() == True && rawtok->str() == PRAGMA && rawtok->next && rawtok->next->str() == ONCE && sameline(rawtok,rawtok->next)) {
                 pragmaOnce.insert(rawtok->location.file());
             }
-            rawtok = gotoNextLine(rawtok);
+            if (ifstates.top() != True && rawtok->nextcond)
+                rawtok = rawtok->nextcond->previous;
+            else
+                rawtok = gotoNextLine(rawtok);
             continue;
         }
 

simplecpp.h

@@ -96,12 +96,12 @@ namespace simplecpp {
     class SIMPLECPP_LIB Token {
     public:
         Token(const TokenString &s, const Location &loc, bool wsahead = false) :
-            whitespaceahead(wsahead), location(loc), previous(nullptr), next(nullptr), string(s) {
+            whitespaceahead(wsahead), location(loc), previous(nullptr), next(nullptr), nextcond(nullptr), string(s) {
             flags();
         }
 
         Token(const Token &tok) :
-            macro(tok.macro), op(tok.op), comment(tok.comment), name(tok.name), number(tok.number), whitespaceahead(tok.whitespaceahead), location(tok.location), previous(nullptr), next(nullptr), string(tok.string), mExpandedFrom(tok.mExpandedFrom) {
+            macro(tok.macro), op(tok.op), comment(tok.comment), name(tok.name), number(tok.number), whitespaceahead(tok.whitespaceahead), location(tok.location), previous(nullptr), next(nullptr), nextcond(nullptr), string(tok.string), mExpandedFrom(tok.mExpandedFrom) {
         }
 
         void flags() {
@@ -137,6 +137,7 @@ namespace simplecpp {
         Location location;
         Token *previous;
         Token *next;
+        mutable const Token *nextcond;
 
         const Token *previousSkipComments() const {
             const Token *tok = this->previous;