[PATCH] Fix ICE caused by swallowing a token in c_parser_consume_token

[Kerem Kat]

Hi,

This patch fixes ICE on invalid code, specifically files that have
conflict-marker-like signs before EOF.

2019-12-30  Kerem Kat  <kerem...@gmail.com>

PR c/92833
gcc/
    * c-parser.c (c_parser_consume_token): Fix peeked
    token stack pop to support 4 available tokens.

    * c-c++-common/pr92833-*.c: New tests.


diff --git a/gcc/c/c-parser.c b/gcc/c/c-parser.cindex
b3763c2e888..572805d6467 100644
--- a/gcc/c/c-parser.c
+++ b/gcc/c/c-parser.c
@@ -846,7 +846,11 @@ c_parser_consume_token (c_parser *parser)
     {
       parser->tokens[0] = parser->tokens[1];
       if (parser->tokens_avail >= 3)
- parser->tokens[1] = parser->tokens[2];
+ {
+  parser->tokens[1] = parser->tokens[2];
+  if (parser->tokens_avail >= 4)
+    parser->tokens[2] = parser->tokens[3];
+ }
     }
   parser->tokens_avail--;
 }
diff --git a/gcc/testsuite/c-c++-common/pr92833-1.c
b/gcc/testsuite/c-c++-common/pr92833-1.c
new file mode 100644
index 00000000000..ab164aae929
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr92833-1.c
@@ -0,0 +1,4 @@
+/* Six marker characters at EOF, causes conflict marker detector to peek 4
+   tokens. */
+
+/* { dg-error "expected" } */ <<<<<<
\ No newline at end of file
diff --git a/gcc/testsuite/c-c++-common/pr92833-2.c
b/gcc/testsuite/c-c++-common/pr92833-2.c
new file mode 100644
index 00000000000..8347f3542b7
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr92833-2.c
@@ -0,0 +1,4 @@
+/* Six marker characters at EOF, causes conflict marker detector to peek 4
+   tokens. */
+
+/* { dg-error "expected" } */ ======
\ No newline at end of file
diff --git a/gcc/testsuite/c-c++-common/pr92833-3.c
b/gcc/testsuite/c-c++-common/pr92833-3.c
new file mode 100644
index 00000000000..fe4f6d4c017
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr92833-3.c
@@ -0,0 +1,4 @@
+/* Six marker characters at EOF, causes conflict marker detector to peek 4
+   tokens. */
+
+/* { dg-error "expected" } */ >>>>>>
\ No newline at end of file
diff --git a/gcc/testsuite/c-c++-common/pr92833-4.c
b/gcc/testsuite/c-c++-common/pr92833-4.c
new file mode 100644
index 00000000000..b591ea9fa15
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr92833-4.c
@@ -0,0 +1,7 @@
+/* Six marker characters at EOF, causes conflict marker detector to peek 4
+   tokens. */
+
+/* { dg-message "expected" "expected" { target *-*-* } .3 } */
+>>
+>>
+>>
\ No newline at end of file