Fix issue #391: input stack underflow on too few macro arguments.

Test/badMacroArgs.frag

@@ -0,0 +1,4 @@
+#version 400
+
+#define m(a) a
+m()

Test/baseResults/badMacroArgs.frag.out

@@ -0,0 +1,7 @@
+badMacroArgs.frag
+Warning, version 400 is not yet complete; most version-specific features are present, but some are missing.
+ERROR: 0:4: 'macro expansion' : Too few args in Macro m
+ERROR: 0:4: '' :  syntax error
+ERROR: 2 compilation errors.  No code generated.
+
+

Test/cppIndent.vert

@@ -58,4 +58,4 @@ sum += 900000000.0;
 
 #define FUNC(a,b)		a+b
 // needs to be last test in file due to syntax error
-void foo986(){	FUNC( (((2)))), 4); }  // ERROR, too many )
+void foo986(){	FUNC( (((2)))), 4); }  // ERROR, too few arguments )

Test/runtests

@@ -18,6 +18,13 @@ fi
 
 rm -f comp.spv frag.spv geom.spv tesc.spv tese.spv vert.spv
 
+#
+# special tests
+#
+
+$EXE badMacroArgs.frag > $TARGETDIR/badMacroArgs.frag.out
+diff -b $BASEDIR/badMacroArgs.frag.out $TARGETDIR/badMacroArgs.frag.out || HASERROR=1
+
 #
 # reflection tests
 #

glslang/MachineIndependent/preprocessor/PpContext.h

@@ -218,7 +218,7 @@ protected:
     TParseContextBase& parseContext;
 
     // Get the next token from *stack* of input sources, popping input sources
-    // that are out of tokens, down until an input sources is found that has a token.
+    // that are out of tokens, down until an input source is found that has a token.
     // Return EndOfInput when there are no more tokens to be found by doing this.
     int scanToken(TPpToken* ppToken)
     {
@@ -226,7 +226,7 @@ protected:
 
         while (! inputStack.empty()) {
             token = inputStack.back()->scan(ppToken);
-            if (token != EndOfInput)
+            if (token != EndOfInput || inputStack.empty())
                 break;
             popInput();
         }