Do not evaluate an untaken ELIF's condition

Fixes gbdev#764
Rangi42 · Mar 22, 2021 · bd3d438 · bd3d438
1 parent 5406674
commit bd3d438
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Showing 4 changed files with 35 additions and 0 deletions.
diff --git a/src/asm/lexer.c b/src/asm/lexer.c
@@ -1856,6 +1856,8 @@ static char const *reportGarbageChar(unsigned char firstByte)
 
 /* Lexer core */
 
+static int yylex_SKIP_TO_ENDC(void); // forward declaration for yylex_NORMAL
+
 static int yylex_NORMAL(void)
 {
 	dbgPrint("Lexing in normal mode, line=%" PRIu32 ", col=%" PRIu32 "\n",
@@ -2085,6 +2087,12 @@ static int yylex_NORMAL(void)
 			if (startsIdentifier(c)) {
 				int tokenType = readIdentifier(c);
 
+				/* An ELIF after a taken IF needs to not evaluate its condition */
+				if (tokenType == T_POP_ELIF && lexerState->lastToken == T_NEWLINE
+				 && lexer_GetIFDepth() > 0 && lexer_RanIFBlock()
+				 && !lexer_ReachedELSEBlock())
+					return yylex_SKIP_TO_ENDC();
+
 				/* If a keyword, don't try to expand */
 				if (tokenType != T_ID && tokenType != T_LOCAL_ID)
 					return tokenType;

diff --git a/test/asm/elif-after-taken-if.asm b/test/asm/elif-after-taken-if.asm
@@ -0,0 +1,23 @@
+if 1
+	println "taken if"
+elif 2 / 0 ; avoided fatal "Division by zero" error
+	println "untaken elif"
+elif 3 / 0 ; avoided fatal "Division by zero" error
+	println "untaken after untaken"
+endc
+
+if 0
+	println "untaken if"
+elif 1
+	println "taken elif"
+elif !@#$ ; avoided fatal syntax error
+	println "untaken elif"
+elif %^&* ; avoided fatal syntax error
+	println "untaken after untaken"
+endc
+
+if 0
+	println "untaken if"
+elif 1 / 0 ; fatal "Division by zero" error
+	println "unreached elif"
+endc
diff --git a/test/asm/elif-after-taken-if.err b/test/asm/elif-after-taken-if.err
@@ -0,0 +1,2 @@
+FATAL: elif-after-taken-if.asm(21):
+    Division by zero
diff --git a/test/asm/elif-after-taken-if.out b/test/asm/elif-after-taken-if.out
@@ -0,0 +1,2 @@
+taken if
+taken elif
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,2 @@
		FATAL: elif-after-taken-if.asm(21):
		Division by zero