RFR: JDK-8221851: Use of THIS_FILE in hotspot invalidates precompiled header on Linux/GCC

[Erik Joelsson]

Hello,

On 2019-04-05 15:46, Kim Barrett wrote:
>> On Apr 5, 2019, at 11:09 AM, Erik Joelsson <erik.joelsson at oracle.com> wrote:
>> So to make it clear. This patch now does the following:
>>
>> * Removes the setting of -DTHIS_FILE=... from all compilation units involved in building Hotspot.
>>
>> * Introduces THIS_FILE as a macro in Hotspot src which gets just the filename from the __FILE__ macro.
>>
>> * Changes the use of the __FILE__/THIS_FILE macro in exceptions.hpp to just always use the new THIS_FILE.
>>
>> * Introduces the use of -fmacro-file-map, when supported by the compiler, to rewrite __FILE__ to a path relative to the workspace root.
>>
>> The two main improvements from this are that precompiled headers should start working with GCC again and when building with GCC 8 or later, we get rid of absolute paths from our binaries.
>>
>> /Erik
> (I've only looked at the src/hotspot changes.)
>
> It's not clear there's a reason to put this_file_helper and THIS_FILE
> anywhere other than in exceptions.hpp. I don't think there's a (known)
> benefit to using it anywhere else. Using a trimmed __FILE__ doesn't
> eliminate the "absolute paths embedded in binaries" problem. For that
> we need -fmacro-file-map or the like (or perhaps give up on absolute
> paths in the build system, but those are pretty useful in the .cmdfile
> files at least).
>
> Assuming all that, consider instead putting this_file_helper in
> exceptions.hpp (perhaps with a better name?), don't bother with
> THIS_FILE, and define THREAD_AND_LOCATION as
>
> #define THREAD_AND_LOCATION THREAD, this_file_helper(__FILE__), __LINE__
>
Moved to exceptions.hpp, renamed to "basename", and removed the 
THIS_FILE macro. Given that Kim will not be able to review this further, 
I'm now looking for another Hotspot reviewer.

http://cr.openjdk.java.net/~erikj/8221851/webrev.04/

/Erik