[Bug c/28649] New: [4.1/4.2 regression] Poor error recovery of C parser

[reichelt at gcc dot gnu dot org]

The error recovery of the C parser sometimes gets confused.
The following testcase contains three bugs:

  void foo()
  {
     +;
     +;
  }

  int +;

But the C frontend only reports the first one:

  bug.c: In function 'foo':
  bug.c:3: error: expected expression before ';' token

The old yacc-based parser reported two bugs, so this is a regression.

  bug.c: In function 'foo':
  bug.c:3: error: parse error before ';' token
  bug.c: At top level:
  bug.c:7: error: parse error before '+' token

The C++ frontend reports all, btw.:

  bug.cc: In function 'void foo()':
  bug.cc:3: error: expected primary-expression before ';' token
  bug.cc:4: error: expected primary-expression before ';' token
  bug.cc: At global scope:
  bug.cc:7: error: expected unqualified-id before '+' token

In other situations we get bogus error messages, e.g.:

  void foo() { +; }
  int i;
  void bar() { i++; }

  bug.c: In function 'foo':
  bug.c:1: error: expected expression before ';' token
  bug.c: In function 'bar':
  bug.c:3: error: 'i' undeclared (first use in this function)
  bug.c:3: error: (Each undeclared identifier is reported only once
  bug.c:3: error: for each function it appears in.)

Posting a patch soon.


-- 
           Summary: [4.1/4.2 regression] Poor error recovery of C parser
           Product: gcc
           Version: 4.2.0
            Status: UNCONFIRMED
          Keywords: diagnostic, monitored
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: reichelt at gcc dot gnu dot org
        ReportedBy: reichelt at gcc dot gnu dot org


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=28649