[SR-452] Recursive function without base case returns garbage value when compiled with -O

[swift-ci]

Previous ID	SR-452
Radar	None
Original Reporter	loic (JIRA User)
Type	Bug

Environment

Swift 2.2-dev (December 31)
OS X El Capitan

Additional Detail from JIRA

Votes	1
Component/s	Compiler
Labels	Bug, OptimizedOnly
Assignee	None
Priority	Medium

md5: 546cfc45f510272795c24cb4aa0daa3d

Issue Description:

This code will crash (segfault) when compiled with -Onone, but returns garbage when compiled with -O.

func rec(x: Int) -> Int {
    return rec(x)
}
print(rec(0))

I think it should always crash.

[swift-ci]

Comment by Nadav Rotem (JIRA)

It looks like _TF4main3recFSiSi is compiled into: return undef.

[swift-ci]

Comment by Nadav Rotem (JIRA)

The SIL looks okay. It looks like LLVM is optimizing _TF4main3recFSiSi into "return undef".

// main.rec (Swift.Int) -> Swift.Int
sil hidden @_TF4main3recFSiSi : $@convention(thin) (Int) -> Int {
bb0(%0 : $Int):
debug_value %0 : $Int // let x // id: %1
// function_ref main.rec (Swift.Int) -> Swift.Int
%2 = function_ref @_TF4main3recFSiSi : $@convention(thin) (Int) -> Int // user: %3
%3 = apply %2(%0) : $@convention(thin) (Int) -> Int // user: %4
return %3 : $Int // id: %4
}

define hidden i64 @_TF4main3recFSiSi(i64) #1 {
entry:
ret i64 undef
}

[Dante-Broggi]

Has this been resolved? If so, it should be closed.