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* [PATCH] C++: less verbose error-recovery for version conflict markers
@ 2018-06-28 18:13 David Malcolm
  2018-06-28 20:22 ` Jason Merrill
  0 siblings, 1 reply; 2+ messages in thread
From: David Malcolm @ 2018-06-28 18:13 UTC (permalink / raw)
  To: gcc-patches; +Cc: David Malcolm

We handle version conflict markers in source:

$ cat /tmp/test.cc

extern void f1 (void);
extern void f2 (void);
extern void f3 (void);
extern void f4 (void);

void test ()
{
  f1 ();
<<<<<<< HEAD
  f2 ();
=======
  f3 ();
>>>>>>> 252be53... Some commit message
  f4 ();
}

The C frontend's output is mostly reasonable:

gcc -xc /tmp/test.cc
/tmp/test.cc: In function ‘test’:
/tmp/test.cc:9:1: error: version control conflict marker in file
 <<<<<<< HEAD
 ^~~~~~~
/tmp/test.cc:11:1: error: version control conflict marker in file
 =======
 ^~~~~~~
/tmp/test.cc:13:1: error: version control conflict marker in file
 >>>>>>> 252be53... Some commit message
 ^~~~~~~
/tmp/test.cc:13:9: error: invalid suffix "be53..." on integer constant
 >>>>>>> 252be53... Some commit message
         ^~~~~~~~~~

whereas in C++ the output can be very verbose:

/tmp/test.cc: In function ‘void test()’:
/tmp/test.cc:9:1: error: version control conflict marker in file
 <<<<<<< HEAD
 ^~~~~~~
/tmp/test.cc:9:3: error: expected primary-expression before ‘<<’ token
 <<<<<<< HEAD
   ^~
/tmp/test.cc:9:5: error: expected primary-expression before ‘<<’ token
 <<<<<<< HEAD
     ^~
/tmp/test.cc:9:7: error: expected primary-expression before ‘<’ token
 <<<<<<< HEAD
       ^
/tmp/test.cc:9:9: error: ‘HEAD’ was not declared in this scope
 <<<<<<< HEAD
         ^~~~
/tmp/test.cc:11:1: error: version control conflict marker in file
 =======
 ^~~~~~~
/tmp/test.cc:11:3: error: expected primary-expression before ‘==’ token
 =======
   ^~
/tmp/test.cc:11:5: error: expected primary-expression before ‘==’ token
 =======
     ^~
/tmp/test.cc:11:7: error: expected primary-expression before ‘=’ token
 =======
       ^
/tmp/test.cc:13:1: error: version control conflict marker in file
 >>>>>>> 252be53... Some commit message
 ^~~~~~~
/tmp/test.cc:13:3: error: expected primary-expression before ‘>>’ token
 >>>>>>> 252be53... Some commit message
   ^~
/tmp/test.cc:13:5: error: expected primary-expression before ‘>>’ token
 >>>>>>> 252be53... Some commit message
     ^~
/tmp/test.cc:13:7: error: expected primary-expression before ‘>’ token
 >>>>>>> 252be53... Some commit message
       ^
/tmp/test.cc:13:9: error: unable to find numeric literal operator ‘operator""be53...’
 >>>>>>> 252be53... Some commit message
         ^~~~~~~~~~

The following patch eliminates this spew by consuming tokens until the
start of the next line after emitting such a message.

The C frontend and C++ with -std=c++98 both emit:
  error: invalid suffix "be53..." on integer constant
on the above testcase, but it's not fixable through this approach,
since that error is emitted by the lexer.


Successfully bootstrapped & regrtested on x86_64-pc-linux-gnu.

OK for trunk?

gcc/cp/ChangeLog:
	* parser.c (cp_parser_error_1): After issuing a conflict marker
	error, consume tokens until the end of the source line.

gcc/testsuite/ChangeLog:
	* g++.dg/conflict-markers-2.C: New test.
---
 gcc/cp/parser.c                           | 14 ++++++++++++++
 gcc/testsuite/g++.dg/conflict-markers-2.C | 17 +++++++++++++++++
 2 files changed, 31 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/conflict-markers-2.C

diff --git a/gcc/cp/parser.c b/gcc/cp/parser.c
index 154729c..09d224f 100644
--- a/gcc/cp/parser.c
+++ b/gcc/cp/parser.c
@@ -2862,6 +2862,20 @@ cp_parser_error_1 (cp_parser* parser, const char* gmsgid,
       if (cp_lexer_peek_conflict_marker (parser->lexer, token->type, &loc))
 	{
 	  error_at (loc, "version control conflict marker in file");
+	  expanded_location token_exploc = expand_location (token->location);
+	  /* Consume tokens until the end of the source line.  */
+	  while (1)
+	    {
+	      cp_lexer_consume_token (parser->lexer);
+	      cp_token *next = cp_lexer_peek_token (parser->lexer);
+	      if (next == NULL)
+		break;
+	      expanded_location next_exploc = expand_location (next->location);
+	      if (next_exploc.file != token_exploc.file)
+		break;
+	      if (next_exploc.line != token_exploc.line)
+		break;
+	    }
 	  return;
 	}
     }
diff --git a/gcc/testsuite/g++.dg/conflict-markers-2.C b/gcc/testsuite/g++.dg/conflict-markers-2.C
new file mode 100644
index 0000000..4fc3820
--- /dev/null
+++ b/gcc/testsuite/g++.dg/conflict-markers-2.C
@@ -0,0 +1,17 @@
+// { dg-do compile { target c++11 } }
+
+extern void f1 (void);
+extern void f2 (void);
+extern void f3 (void);
+extern void f4 (void);
+
+void test ()
+{
+  f1 ();
+<<<<<<< HEAD // { dg-error "conflict marker" }
+  f2 ();
+======= // { dg-error "conflict marker" }
+  f3 ();
+>>>>>>> 252be53... Some commit message // { dg-error "conflict marker" }
+  f4 ();
+}
-- 
1.8.5.3

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2018-06-28 18:13 [PATCH] C++: less verbose error-recovery for version conflict markers David Malcolm
2018-06-28 20:22 ` Jason Merrill

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