Currently when calling clone with some unsupported flags you get: ==3508066== Unsupported clone() flags: 0x100111 ==3508066== ==3508066== The only supported clone() uses are: ==3508066== - via a threads library (LinuxThreads or NPTL) ==3508066== - via the implementation of fork or vfork ==3508066== ==3508066== Valgrind detected that your program requires ==3508066== the following unimplemented functionality: ==3508066== Valgrind does not support general clone(). ==3508066== This may be because the functionality is hard to implement, ==3508066== or because no reasonable program would behave this way, ==3508066== or because nobody has yet needed it. In any case, let us know at ==3508066== www.valgrind.org and/or try to work around the problem, if you can. ==3508066== ==3508066== Valgrind has to exit now. Sorry. Bye! This doesn't immediately make clear which clone flags are problematic. In practice it is only a problem for some combination(s) of CLONE_VM CLONE_FS CLONE_FILES and CLONE_VFORK. It would be good if the error messages decoded the clone flags and said precisely what the problematic flag was.
Created attachment 183086 [details] Better report which clone flag are problematic With this patch valgrind now reports: ==3404273== Unsupported clone() flags: 0x100111 ==3404273== ==3404273== The only supported clone() uses are: ==3404273== - via a threads library (VM, FS and FILES flags set) ==3404273== - via the implementation of vfork (VFORK or VFORK and VM flags set) ==3404273== - via plain fork (no VM, FS, FILES, VFORK flags set) ==3404273== clone call had CLONE_VM flags set ==3404273== ==3404273== Valgrind detected that your program requires ==3404273== the following unimplemented functionality: ==3404273== Valgrind does not support general clone(). ==3404273== This may be because the functionality is hard to implement, ==3404273== or because no reasonable program would behave this way, ==3404273== or because nobody has yet needed it. In any case, let us know at ==3404273== www.valgrind.org and/or try to work around the problem, if you can. ==3404273== ==3404273== Valgrind has to exit now. Sorry. Bye!
commit 1f39c9582bc6ca4470b202c6b61d477ec3abfce7 Author: Mark Wielaard <mark@klomp.org> Date: Wed Jul 9 13:04:51 2025 +0200 Better report which clone flag are problematic Be explict about which combination of CLONE_VM, CLONE_FS, CLONE_FILES and CLONE_VFORK flags are supported and which combination isn't. https://bugs.kde.org/show_bug.cgi?id=506795