> On Jan 3, 2024, at 7:16 AM, Baesken, Matthias <matthias.baes...@sap.com> > wrote: > > Btw. I found this rather recent discussion about reverting the forcing > of setting -std=gnu++11 in autoconf : > > https://urldefense.com/v3/__https://mail.gnu.org/archive/html/bug-autoconf/2023-12/msg00073.html__;!!ACWV5N9M2RV99hQ!KfFeVOARPmr8RlTN3t2qMgkljzWkcpqA_NwxnyMtkaHzz3dwDxZjVsZZZvQLEXP-Rd6rngZKnovzj0C6Uzn-XF_4Gw$ > https://urldefense.com/v3/__https://savannah.gnu.org/support/?110879__;!!ACWV5N9M2RV99hQ!KfFeVOARPmr8RlTN3t2qMgkljzWkcpqA_NwxnyMtkaHzz3dwDxZjVsZZZvQLEXP-Rd6rngZKnovzj0C6Uzk4Umn7ug$ > > revert forcing/setting -std=gnu++11 by default (introduced in Autoconf 2.70)
So autoconf forcibly selects a -std= option, possibly overriding either an explicit option or the compiler's default. Who thought that was a good idea? There are even comments from the time that question that "feature". It looks like there is code to attempt to deal with that sort of thing in our build system. See TOOLCHAIN_POST_DETECTION in make/autoconf/toolchain.m4. That dates back to JDK 9. However, that only deals with CFLAGS and CXXFLAGS. The AC_PROG_CC/CXX feature affects the CC/CXX variables. Bleh! But I wonder why our explicit -std=gnu++98 (or whatever we were using) doesn't override that. In the command lines are you seeing "g++ ... -std=gnu++11 ... -std=c++14" I'm also not sure what will happen with later JDK versions that specify -std=c++14. I have no idea why disabling PCH might change things in this area.
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