Files
Nim/tests/cpp/tmanual_exception.nim
ringabout e6f6c369ff fixes bugs on the Nim manual (#24669)
ref https://en.cppreference.com/w/cpp/error/exception/what

> Pointer to a null-terminated string with explanatory information. The
pointer is guaranteed to be valid at least until the exception object
from which it is obtained is destroyed, or until a non-const member
function on the exception object is called.

The pointer is only valid before `CStdException as e` is destroyed


Old examples are broken on macOS arm64

```
/Users/blue/Desktop/nimony/test4.nim(38) test4
/Users/blue/Desktop/nimony/test4.nim(26) fn
/Users/blue/.choosenim/toolchains/nim-#devel/lib/std/assertions.nim(41) failedAssertImpl
/Users/blue/.choosenim/toolchains/nim-#devel/lib/std/assertions.nim(36) raiseAssert
/Users/blue/.choosenim/toolchains/nim-#devel/lib/system/fatal.nim(53) sysFatal
Error: unhandled exception: /Users/blue/Desktop/nimony/test4.nim(26, 3) `$b == "foo2"`  [AssertionDefect]
```
2025-02-06 23:19:53 +01:00

37 lines
1.1 KiB
Nim

discard """
targets: cpp
"""
# manual example
type
CStdException {.importcpp: "std::exception", header: "<exception>", inheritable.} = object
## does not inherit from `RootObj`, so we use `inheritable` instead
CRuntimeError {.requiresInit, importcpp: "std::runtime_error", header: "<stdexcept>".} = object of CStdException
## `CRuntimeError` has no default constructor => `requiresInit`
proc what(s: CStdException): cstring {.importcpp: "((char *)#.what())".}
proc initRuntimeError(a: cstring): CRuntimeError {.importcpp: "std::runtime_error(@)", constructor.}
proc initStdException(): CStdException {.importcpp: "std::exception()", constructor.}
proc fn() =
let a = initRuntimeError("foo")
doAssert $a.what == "foo"
var b = ""
try: raise initRuntimeError("foo2")
except CStdException as e:
doAssert e is CStdException
b = $e.what()
doAssert b == "foo2"
try: raise initStdException()
except CStdException: discard
try: raise initRuntimeError("foo3")
except CRuntimeError as e:
b = $e.what()
except CStdException:
doAssert false
doAssert b == "foo3"
fn()