[LLVMbugs] [Bug 12183] New: Assertion failure: "Functions without a prototype cannot be overloaded"

[bugzilla-daemon at llvm.org]

http://llvm.org/bugs/show_bug.cgi?id=12183

             Bug #: 12183
           Summary: Assertion failure: "Functions without a prototype
                    cannot be overloaded"
           Product: clang
           Version: trunk
          Platform: PC
        OS/Version: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: Frontend
        AssignedTo: unassignedclangbugs at nondot.org
        ReportedBy: clint at clintcaywood.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified


Created attachment 8142
  --> http://llvm.org/bugs/attachment.cgi?id=8142
10 line file that will crash clang

Trunk revision 152011.

In release mode this causes a segmentation fault, but we get the assertion
failure if those are enabled:

This example code shouldn't compile, but the compiler crashing on it is a bit
dramatic. I believe it it has something to do with clang implicitly building
overloads for function used_before_declared because it is first used with a
known type, then with an undefined type. This sets it up to be in a bad state
next time it is referenced.

If we switch the positions of foo and used_before_declared, everything is fine.
Likewise if we use a defined type for its parameter.

======================
int foo()
{
    return used_before_declared(0);
}

int used_before_declared(undefined_type err)
{

}

void bar()
{
    used_before_declared(0); // Will crash here
}

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