RFR: 8329257: AIX: Switch HOTSPOT_TOOLCHAIN_TYPE from xlc to gcc [v3]

[Magnus Ihse Bursie]

On Tue, 30 Apr 2024 09:36:52 GMT, Joachim Kern <jkern at openjdk.org> wrote:

>> On AIX `stdlib.h` also would define `alloca`, if `__STRICT_ANSI__` wouldn't be set. 
>> 
>> 
>> 780 #if !defined(__xlC__) || defined(__ibmxl__) || defined(__cplusplus)
>> 781 #if defined(__IBMCPP__) && !defined(__ibmxl__)
>> 782    extern "builtin" char *__alloca (size_t);
>> 783 #  define alloca __alloca
>> 784 #elif defined(__GNUC__) && !defined(__STRICT_ANSI__)
>> 785    #undef  alloca
>> 786    #define alloca(size)   __builtin_alloca (size)
>> 787 #endif
>> 
>> 
>> A small plain Testprogramm not using all of the flags we used in jdk build, does not set `__STRICT_ANSI__` and then `alloca` is defined correct.
>
> The compiler flag introducing __STRICT_ANSI__ is -std=c++14. If I omit this explicit compiler flag the default is used, which is also c++14. But the default does not set __STRICT_ANSI__ but 2 other defines. I will try a build without -std=c++14 and if this works, we have a solution. Nevertheless i will interrogate IBM what the hell this behavior should be.

I don't think leaving out `-std=c++14` for AIX is a good solution.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18536#discussion_r1584529538