EXT_debug_printf - make escape sequences better match C/C++

Test/baseResults/spv.debugPrintf.frag.out

 spv.debugPrintf.frag
 // Module Version 10000
 // Generated by (magic number): 80008
-// Id's are bound by 13
+// Id's are bound by 17
 
                               Capability Shader
                               Extension  "SPV_KHR_non_semantic_info"
@@ -11,6 +11,8 @@ spv.debugPrintf.frag
                               EntryPoint Fragment 4  "main"
                               ExecutionMode 4 OriginUpperLeft
                6:             String  "ASDF \ ? \ %d %d %d"
+              13:             String  "ABAZ"
+              15:             String  "B#$B1Z"
                               Source GLSL 450
                               SourceExtension  "GL_EXT_debug_printf"
                               Name 4  "main"
@@ -23,5 +25,7 @@ spv.debugPrintf.frag
          4(main):           2 Function None 3
                5:             Label
               12:           2 ExtInst 11(NonSemantic.DebugPrintf) 1(DebugPrintf) 6 8 9 10
+              14:           2 ExtInst 11(NonSemantic.DebugPrintf) 1(DebugPrintf) 13
+              16:           2 ExtInst 11(NonSemantic.DebugPrintf) 1(DebugPrintf) 15
                               Return
                               FunctionEnd

Test/baseResults/spv.debugPrintf_Error.frag.out

+spv.debugPrintf_Error.frag
+ERROR: 0:7: 'string' : Expected hex value in escape sequence 
+ERROR: 0:10: 'string' : Invalid escape sequence 
+ERROR: 2 compilation errors.  No code generated.
+
+
+SPIR-V is not generated for failed compile or link

Test/spv.debugPrintf.frag

@@ -4,4 +4,10 @@
 void main()
 {
     debugPrintfEXT("ASDF \\ \? \x5C %d %d %d", 1, 2, 3);
+
+    // ABA{backspace}Z
+    debugPrintfEXT("\x41\x000042\x41\x8Z");
+
+    // B#${bell, aka \a}B1Z
+    debugPrintfEXT("\102\043\44\7\1021Z");
 }

Test/spv.debugPrintf_Error.frag

+#version 450
+#extension GL_EXT_debug_printf : enable
+
+void main()
+{
+    // invalid hex sequence
+    debugPrintfEXT("\xZ");
+
+    // not an octal sequence
+    debugPrintfEXT("\8");
+}

glslang/MachineIndependent/preprocessor/PpScanner.cpp

@@ -1045,28 +1045,31 @@ int TPpContext::tStringInput::scan(TPpToken* ppToken)
                         case 't':  ch = 0x09; break;
                         case 'v':  ch = 0x0b; break;
                         case 'x': 
-                            // two character hex value
-                            nextCh = getch();
-                            if (nextCh >= '0' && nextCh <= '9')
-                                nextCh -= '0';
-                            else if (nextCh >= 'A' && nextCh <= 'F')
-                                nextCh -= 'A' - 10;
-                            else if (nextCh >= 'a' && nextCh <= 'f')
-                                nextCh -= 'a' - 10;
-                            else
-                                pp->parseContext.ppError(ppToken->loc, "Expected hex value in escape sequence", "string", "");
-                            ch = nextCh * 0x10;
-                            nextCh = getch();
-                            if (nextCh >= '0' && nextCh <= '9')
-                                nextCh -= '0';
-                            else if (nextCh >= 'A' && nextCh <= 'F')
-                                nextCh -= 'A' - 10;
-                            else if (nextCh >= 'a' && nextCh <= 'f')
-                                nextCh -= 'a' - 10;
-                            else
-                                pp->parseContext.ppError(ppToken->loc, "Expected hex value in escape sequence", "string", "");
-                            ch += nextCh;
-                            break;
+                            // Hex value, arbitrary number of characters. Terminated by the first
+                            // non-hex digit
+                            {
+                                int numDigits = 0;
+                                ch = 0;
+                                while (true) {
+                                    nextCh = getch();
+                                    if (nextCh >= '0' && nextCh <= '9')
+                                        nextCh -= '0';
+                                    else if (nextCh >= 'A' && nextCh <= 'F')
+                                        nextCh -= 'A' - 10;
+                                    else if (nextCh >= 'a' && nextCh <= 'f')
+                                        nextCh -= 'a' - 10;
+                                    else {
+                                        ungetch();
+                                        break;
+                                    }
+                                    numDigits++;
+                                    ch = ch * 0x10 + nextCh;
+                                }
+                                if (numDigits == 0) {
+                                    pp->parseContext.ppError(ppToken->loc, "Expected hex value in escape sequence", "string", "");
+                                }
+                                break;
+                            }
                         case '0':
                         case '1':
                         case '2':
@@ -1075,20 +1078,23 @@ int TPpContext::tStringInput::scan(TPpToken* ppToken)
                         case '5':
                         case '6':
                         case '7':
-                            // three character octal value
-                            nextCh = getch() - '0';
-                            if (nextCh > 3)
-                                pp->parseContext.ppError(ppToken->loc, "Expected octal value in escape sequence", "string", "");
-                            ch = nextCh * 8 * 8;
-                            nextCh = getch() - '0';
-                            if (nextCh > 7)
-                                pp->parseContext.ppError(ppToken->loc, "Expected octal value in escape sequence", "string", "");
-                            ch += nextCh * 8;
-                            nextCh = getch() - '0';
-                            if (nextCh > 7)
-                                pp->parseContext.ppError(ppToken->loc, "Expected octal value in escape sequence", "string", "");
-                            ch += nextCh;
-                            break;
+                            // Octal value, up to three octal digits
+                            {
+                                int numDigits = 1;
+                                ch = nextCh - '0';
+                                while (numDigits < 3) {
+                                    nextCh = getch();
+                                    if (nextCh >= '0' && nextCh <= '7')
+                                        nextCh -= '0';
+                                    else {
+                                        ungetch();
+                                        break;
+                                    }
+                                    numDigits++;
+                                    ch = ch * 8 + nextCh;
+                                }
+                                break;
+                            }
                         default:
                             pp->parseContext.ppError(ppToken->loc, "Invalid escape sequence", "string", "");
                             break;

gtests/Spv.FromFile.cpp

@@ -310,6 +310,7 @@ INSTANTIATE_TEST_CASE_P(
         "spv.dataOutIndirect.frag",
         "spv.dataOutIndirect.vert",
         "spv.debugPrintf.frag",
+        "spv.debugPrintf_Error.frag",
         "spv.demoteDisabled.frag",
         "spv.deepRvalue.frag",
         "spv.depthOut.frag",