[LLVMbugs] [Bug 24005] New: Clang exception handling: wrong IR generation - no cleanup for array of memcpy-able objects in struct

[bugzilla-daemon at llvm.org]

https://llvm.org/bugs/show_bug.cgi?id=24005

            Bug ID: 24005
           Summary: Clang exception handling: wrong IR generation - no
                    cleanup for array of memcpy-able objects in struct
           Product: clang
           Version: trunk
          Hardware: PC
                OS: Windows NT
            Status: NEW
          Severity: normal
          Priority: P
         Component: Frontend
          Assignee: unassignedclangbugs at nondot.org
          Reporter: d.zobnin.bugzilla at gmail.com
                CC: llvmbugs at cs.uiuc.edu
    Classification: Unclassified

When compiling the following test:

struct A {
  int x;
  A() { x = 10; }
  ~A () { x = 20; }
};

struct B {
  B () {}
  B (const B &) {
    throw 1;
  }
};

struct C {
  A a[2];
  B b;
};

int main () {
  try {
    C c1;
    C c2(c1);
  }
  catch (...) {
    return 1;
  }
  return 0;
}

$ clang -cc1 -fexceptions -fcxx-exceptions -O0 test.cpp -emit-llvm -o test.ll

Clang generates the following IR for the copy-ctor of C:

entry:
  %this.addr = alloca %struct.C*, align 8
  %.addr = alloca %struct.C*, align 8
  store %struct.C* %this, %struct.C** %this.addr, align 8
  store %struct.C* %0, %struct.C** %.addr, align 8
  %this1 = load %struct.C*, %struct.C** %this.addr
  %a = getelementptr inbounds %struct.C, %struct.C* %this1, i32 0, i32 0
  %1 = load %struct.C*, %struct.C** %.addr
  %a2 = getelementptr inbounds %struct.C, %struct.C* %1, i32 0, i32 0
  %2 = bitcast [2 x %struct.A]* %a to i8*
  %3 = bitcast [2 x %struct.A]* %a2 to i8*
  call void @llvm.memcpy.p0i8.p0i8.i64(i8* %2, i8* %3, i64 8, i32 4, i1 false)
  %b = getelementptr inbounds %struct.C, %struct.C* %this1, i32 0, i32 1
  %4 = load %struct.C*, %struct.C** %.addr, align 8
  %b3 = getelementptr inbounds %struct.C, %struct.C* %4, i32 0, i32 1
  call void @_ZN1BC1ERKS_(%struct.B* %b, %struct.B* dereferenceable(1) %b3)
  ret void


So the copy-ctor of struct B is called, not invoked, and there are no landing
pads and cleanups for previously constructed objects, no calls for ~A().

Denis Zobnin
=============
Software Engineer
Intel Compiler Team
Intel

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