mcpp's xlings invocations do not inherit XLINGS_ACTIVE_SUBOS (2026.9.14.3) - #638
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…UBOS (2026.9.14.3) A shell that ran `xlings subos use <name>` exports XLINGS_ACTIVE_SUBOS, and xlings ranks it above a home's own `activeSubos`. It names a SubOS of the shell's xlings home; mcpp's registry is a different home, whose tool and view paths mcpp derives from `subos/default`. Inherited, the variable made the registry install mcpp's tools and a project's payloads into a SubOS of the shell's name: on 2026.9.14.2 a fresh home's ninja and patchelf landed in registry/subos/<name>/bin, and the pkg-config view mcpp::pkg_config_libdir() names stayed empty. Found by the sandbox verification of #634 (A7). invocation_env() now decides the variable absent for every invocation; the POSIX prefix renders `env -u XLINGS_ACTIVE_SUBOS`, and ScopedInvocationEnv removes it on Windows for the invocation and restores it afterwards (the guard now saves every scope variable rather than one). Unit XlingsInvocationEnv.TheShellsActiveSubosIsNeverInherited; e2e 686, which fails on 2026.9.14.2 and passes here. Version group 1 moves to 2026.9.14.3.
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mcpp's xlings invocations no longer inherit
XLINGS_ACTIVE_SUBOS. Found by the sandbox verification of #634 (item A7), after 2026.9.14.2 was released.The defect
A shell that ran
xlings subos use <name>(with or without--sandbox) exportsXLINGS_ACTIVE_SUBOS=<name>, and xlings ranks that variable above a home's ownactiveSubos(xlingssrc/core/config.cppm,resolve_subos_scope_). The variable names a SubOS of the shell's xlings home. mcpp's registry is a different home, and mcpp derives its tool, sysroot and pkg-config view paths fromsubos/default. mcpp passed the variable through to its own xlings, so the registry acted on a SubOS of the shell's name.Measured on the released 2026.9.14.2, fresh
MCPP_HOME,mcpp self env:registry/subos/elfpatch,ninja,patchelf)XLINGS_ACTIVE_SUBOS=m634leakcurrent default m634leaksubos/m634leak/bin;subos/default/binholds onlyxlingscurrent defaultsubos/default/binIn the #634 sandbox, a project's
xim:gtk4payloads were installed intoregistry/subos/<name>/, and the viewmcpp::pkg_config_libdir()names (subos/default/usr/lib/pkgconfig) did not exist, sopkg-config gtk4found nothing.The change
invocation_env()decidesXLINGS_ACTIVE_SUBOSabsent for every invocation, global and project mode. The POSIX prefix renders it asenv -u XLINGS_ACTIVE_SUBOS.ScopedInvocationEnvapplies every scope variable on Windows (previously onlyXLINGS_PROJECT_DIR) and restores each after the invocation.XLINGS_SUBOS_LIBopt-out, which has the same cause. CHANGELOG; version group 1 moves to 2026.9.14.3.Tests
XlingsInvocationEnv.TheShellsActiveSubosIsNeverInherited: the decision in both modes, the process environment restored on Windows;ThePosixPrefixRendersTheDecisionreads the new prefix.fresh-sandbox): a fresh home's first command with the variable set creates noregistry/subos/<name>, and its tools are insubos/default/bin. Local: fails on 2026.9.14.2 (A: the registry acted on the shell's SubOS (bin: elfpatch ninja patchelf)), passes on this branch.