Fix issue #708: token pasting within macro argument expansion.

glslang/MachineIndependent/preprocessor/Pp.cpp

@@ -979,25 +979,13 @@ int TPpContext::scanHeaderName(TPpToken* ppToken, char delimit)
 // Returns nullptr if no expanded argument is created.
 TPpContext::TokenStream* TPpContext::PrescanMacroArg(TokenStream& arg, TPpToken* ppToken, bool newLineOkay)
 {
-    // pre-check, to see if anything in the argument needs to be expanded,
-    // to see if we can kick out early
-    int token;
-    RewindTokenStream(arg);
-    do {
-        token = ReadToken(arg, ppToken);
-        if (token == PpAtomIdentifier && lookupMacroDef(atomStrings.getAtom(ppToken->name)) != nullptr)
-            break;
-    } while (token != EndOfInput);
-
-    // if nothing needs to be expanded, kick out early
-    if (token == EndOfInput)
-        return nullptr;
-
     // expand the argument
     TokenStream* expandedArg = new TokenStream;
     pushInput(new tMarkerInput(this));
     pushTokenStreamInput(arg);
+    int token;
     while ((token = scanToken(ppToken)) != tMarkerInput::marker && token != EndOfInput) {
+        token = tokenPaste(token, *ppToken);
         if (token == PpAtomIdentifier && MacroExpand(ppToken, false, newLineOkay) != 0)
             continue;
         RecordToken(*expandedArg, token, ppToken);
@@ -1263,7 +1251,7 @@ int TPpContext::MacroExpand(TPpToken* ppToken, bool expandUndef, bool newLineOka
         }
 
         // We need both expanded and non-expanded forms of the argument, for whether or
-        // not token pasting is in play.
+        // not token pasting will be applied later when the argument is consumed next to ##.
         for (size_t i = 0; i < in->mac->args.size(); i++)
             in->expandedArgs[i] = PrescanMacroArg(*in->args[i], ppToken, newLineOkay);
     }

glslang/MachineIndependent/preprocessor/PpTokens.cpp

@@ -275,19 +275,37 @@ int TPpContext::tTokenInput::scan(TPpToken* ppToken)
     return pp->ReadToken(*tokens, ppToken);
 }
 
-// We are pasting if the entire macro is preceding a pasting operator
-// (lastTokenPastes) and we are also on the last token.
+// We are pasting if
+//   1. we are preceding a pasting operator within this stream
+// or
+//   2. the entire macro is preceding a pasting operator (lastTokenPastes)
+//      and we are also on the last token
 bool TPpContext::tTokenInput::peekPasting()
 {
+    // 1. preceding ##?
+
+    size_t savePos = tokens->current;
+    int byte;
+    // skip white space
+    do {
+        byte = pp->lReadByte(*tokens);
+    } while (byte == ' ');
+    bool pasting = (byte == ((PpAtomPaste & 0x7f) + 0x80));
+    tokens->current = savePos;
+    if (pasting)
+        return true;
+
+    // 2. last token and we've been told after this there will be a ##
+
     if (! lastTokenPastes)
         return false;
-    // Getting here means the last token will be pasted.
+    // Getting here means the last token will be pasted, after this
 
     // Are we at the last non-whitespace token?
-    size_t savePos = tokens->current;
+    savePos = tokens->current;
     bool moreTokens = false;
     do {
-        int byte = pp->lReadByte(*tokens);
+        byte = pp->lReadByte(*tokens);
         if (byte == EndOfInput)
             break;
         if (byte != ' ') {