Runtime safety (panic interface, slices)

doc/langref/test_basic_slices.zig

@@ -44,4 +44,4 @@ test "basic slices" {
     // asserts that the slice has len > 0.
 }
 
-// test_safety=index out of bounds
+// test_safety=index 10 out of bounds of length 4

doc/langref/test_intCast_builtin.zig

@@ -5,4 +5,4 @@ test "integer cast panic" {
     _ = b;
 }
 
-// test_error=cast truncated bits
+// test_error=cast to 'u8' from 'u16' truncated bits: 43981 above 'u8' maximum (255)

doc/langref/test_setRuntimeSafety_builtin.zig

@@ -20,5 +20,5 @@ test "@setRuntimeSafety" {
     }
 }
 
-// test_safety=integer overflow
+// test_safety=add overflowed
 // optimize=ReleaseFast

lib/c.zig

@@ -60,6 +60,17 @@ pub fn panic(msg: []const u8, error_return_trace: ?*std.builtin.StackTrace, _: ?
         else => std.os.abort(),
     }
 }
+/// TODO: Rename to `panic` when old interface is removed.
+pub fn panic2(comptime _: std.builtin.PanicCause, data: anytype) noreturn {
+    @setCold(true);
+    if (builtin.is_test) {
+        std.debug.panic("{any}", .{data});
+    }
+    switch (native_os) {
+        .freestanding, .other, .amdhsa, .amdpal => while (true) {},
+        else => std.os.abort(),
+    }
+}
 
 extern fn main(argc: c_int, argv: [*:null]?[*:0]u8) c_int;
 fn wasm_start() callconv(.C) void {

lib/compiler_rt.zig

@@ -1,6 +1,6 @@
 const builtin = @import("builtin");
 
-pub const panic = @import("compiler_rt/common.zig").panic;
+pub const panic2 = @import("compiler_rt/common.zig").panic2;
 
 comptime {
     // Integer routines

lib/compiler_rt/common.zig

@@ -65,16 +65,10 @@ pub const gnu_f16_abi = switch (builtin.cpu.arch) {
 
 pub const want_sparc_abi = builtin.cpu.arch.isSPARC();
 
-// Avoid dragging in the runtime safety mechanisms into this .o file,
-// unless we're trying to test compiler-rt.
-pub fn panic(msg: []const u8, error_return_trace: ?*std.builtin.StackTrace, _: ?usize) noreturn {
-    _ = error_return_trace;
-    if (builtin.is_test) {
-        @setCold(true);
-        std.debug.panic("{s}", .{msg});
-    } else {
-        unreachable;
-    }
+/// TODO: Rename to `panic` when old interface is removed.
+pub fn panic2(_: std.builtin.PanicCause, _: anytype) noreturn {
+    @setRuntimeSafety(false);
+    unreachable;
 }
 
 /// AArch64 is the only ABI (at the moment) to support f16 arguments without the