Crash on invalid ptrCast

[gwenzek]

Zig Version

0.10.0-dev+138623c8

Steps to Reproduce

Sorry cuda code again, but since cuModuleLoad is an extern symbol it should work with simpler code.
I'll try to reduce this further once I have a chance.

pub extern fn cuModuleLoad(module: [*c]CUmodule, fname: [*c]const u8) CUresult;

test "load_module" {
    const kernel_ptx_path: [:0]const u8 = "kernel.ptx";
    var m: cu.CUmodule = undefined;
    _ = cu.cuModuleLoad(&m, kernel_ptx_path.ptr);
}

test "load_module bad ptr cast" {
    const kernel_ptx_path: [:0]const u8 = "kernel.ptx";
    var m: cu.CUmodule = undefined;
    _ = cu.cuModuleLoad(&m, @ptrCast([*c]const u8, kernel_ptx_path));
}

Expected Behavior

I'd expect the first test to compile and run successfully.
I'd expect the second test to fail to compile with a proper error message

Actual Behavior

The first test compile and run succesfully
The second test triggers an assertion error in the backend.

thread 61164 panic: reached unreachable code
???:?:?: 0x709e51a in assert (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x70fe044 in slicePtrFieldType (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x73f75ef in lowerValue (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x7a25b6d in resolveInst (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x7a5ec1e in airCall (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x77a445f in genBody (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x779f1e0 in updateFunc (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x77a7262 in updateFunc (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x75dd87d in updateFunc (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x73d0ca0 in ensureFuncBodyAnalyzed (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x73cec53 in processOneJob (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x72b53da in performAllTheWork (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x72b1c1b in update (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x72dd046 in updateModule (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x7085f1c in buildOutputType (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x7063f49 in mainArgs (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
???:?:?: 0x734ba87 in main (/home/guw/github/zig-bootstrap/zig/src/zig_llvm.cpp)
error: test...

I had this bug in my code for a long time and it was compiling fine on be94487

[Vexu]

Reduction:

test {
    const s: [:0]const u8 = "foo";
    var p = @ptrCast([*c]const u8, s);
    _ = p;
}

should compile successfully like it does if you change the first const to var.

[gwenzek]

Damn, you're fast. Thanks for the reduction. I tried w/o the function call, but it was getting optimized away