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

[Kevin Walls]

Hi Kim -

Good question. 8-)  Yes the same code is there in the latest version 
when I looked, but address os::current_stack_pointer() is within an 
#ifndef AMD64, so I suspect have we never built 32-bit with the later 
VS2017 compiler...

More file context around the 8u suggestion below..

Thanks
Kevin

src/os_cpu/windows_x86/vm/os_windows_x86.cpp

    452
    453  #ifndef AMD64
    454  // Returns an estimate of the current stack pointer. Result 
must be guaranteed
    455  // to point into the calling threads stack, and be no lower 
than the current
    456  // stack pointer.
    457  #if defined(_MSC_VER) && _MSC_VER >= 1900
    458  // warning C4172: returning address of local variable or 
temporary: dummy
    459  #pragma warning( push )
    460  #pragma warning( disable: 4172 )
    461  #endif
    462  address os::current_stack_pointer() {
    463    int dummy;
    464    address sp = (address)&dummy;
    465    return sp;
    466  }
    467  #if defined(_MSC_VER) && _MSC_VER >= 1900
    468  #pragma warning( pop )
    469  #endif
    470  #else
    471  // Returns the current stack pointer. Accurate value needed for
    472  // os::verify_stack_alignment().
    473  address os::current_stack_pointer() {
    474    typedef address get_sp_func();
    475    get_sp_func* func = CAST_TO_FN_PTR(get_sp_func*,
    476 StubRoutines::x86::get_previous_sp_entry());
    477    return (*func)();
    478  }
    479  #endif
    480




On 06/07/2018 21:09, Kim Barrett wrote:
>> 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().
>