RFR: 8206454: [8u] os::current_stack_pointer() fails to compile on later Windows compilers (warning C4172: returning address of local variable)

[Kim Barrett]

> On Jul 6, 2018, at 5:54 AM, Kevin Walls <kevin.walls at oracle.com> wrote:
> 
> Hi,
> 
> I'd like to get a review of this change for 8u:
> 
> 8206454: [8u] os::current_stack_pointer() fails to compile on later Windows compilers (warning C4172: returning address of local variable)
> https://bugs.openjdk.java.net/browse/JDK-8206454
> 
> This is part of getting jdk8u to accept later Windows compilers. Not changing the code, but adding a conditional  #pragma to let the compiler accept the code.

Why is this only being done for jdk8u, and why isn’t it a problem in (say) jdk11 or jdk12?
The code being patched below is still the same.

> I'll include a diff in text below (can do a webrev if anybody would like one...).
> 
> Many thanks!
> Kevin
> 
> 
> bash-4.2$ hg diff src/os_cpu/windows_x86/vm/os_windows_x86.cpp
> diff -r 5792d995ed26 src/os_cpu/windows_x86/vm/os_windows_x86.cpp
> --- a/src/os_cpu/windows_x86/vm/os_windows_x86.cpp      Wed Jun 27 03:04:33 2018 -0700
> +++ b/src/os_cpu/windows_x86/vm/os_windows_x86.cpp      Fri Jul 06 02:46:48 2018 -0700
> @@ -454,11 +454,19 @@
>  // Returns an estimate of the current stack pointer. Result must be guaranteed
>  // to point into the calling threads stack, and be no lower than the current
>  // stack pointer.
> +#if defined(_MSC_VER) && _MSC_VER >= 1900
> +// warning C4172: returning address of local variable or temporary: dummy
> +#pragma warning( push )
> +#pragma warning( disable: 4172 )
> +#endif
>  address os::current_stack_pointer() {
>    int dummy;
>    address sp = (address)&dummy;
>    return sp;
>  }
> +#if defined(_MSC_VER) && _MSC_VER >= 1900
> +#pragma warning( pop )
> +#endif
>  #else
>  // Returns the current stack pointer. Accurate value needed for
>  // os::verify_stack_alignment().