[LLVMbugs] [Bug 12159] New: Feature request: exit funnels

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=12159

             Bug #: 12159
           Summary: Feature request: exit funnels
           Product: clang
           Version: unspecified
          Platform: Macintosh
        OS/Version: MacOS X
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: Frontend
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: kyle at omnigroup.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


I would like to propose a language extension that would cause all exits from a
block to funnel through another block (except if an exception were raised
during execution of the block).

Imagine the following syntax:

void f(int b) {
  after {
    printf("Inside f");

    if (b > 0)
      return;

    printf("Still inside f");
    b += 100;
  } do {
    printf("Leaving f; b is %d", b);
  }
}

All code paths that leave the after block normally will enter the following do
block. Exceptions will _not_ enter the do block; if you want to handle
exceptions, you would need to use your language's exception handling syntax.
Note that the variable b is visible within the do block; all variables at the
scope of the after block are visible within the corresponding do block.

I would also like to extend this syntax to functions, to help provide contract
programming features:

after void f(int b) {

  int did_log = 0;
  if (b > 0)
    break;

  printf("Logging!");
  did_log = 1;
} do {
  assert(!b || did_log);
}

-- 
Configure bugmail: http://llvm.org/bugs/userprefs.cgi?tab=email
------- You are receiving this mail because: -------
You are on the CC list for the bug.