Date: Fri, 11 Nov 2022 15:04:11 GMT From: Mark Johnston <markj@FreeBSD.org> To: src-committers@FreeBSD.org, dev-commits-src-all@FreeBSD.org, dev-commits-src-main@FreeBSD.org Subject: git: 719e307f80c7 - main - bhyve: Cast away const when fetching a config nvlist Message-ID: <202211111504.2ABF4BbO094243@gitrepo.freebsd.org>
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The branch main has been updated by markj: URL: https://cgit.FreeBSD.org/src/commit/?id=719e307f80c724a39814557e35ac890c75dcd402 commit 719e307f80c724a39814557e35ac890c75dcd402 Author: Mark Johnston <markj@FreeBSD.org> AuthorDate: 2022-11-11 15:02:42 +0000 Commit: Mark Johnston <markj@FreeBSD.org> CommitDate: 2022-11-11 15:02:42 +0000 bhyve: Cast away const when fetching a config nvlist Silence a warning from the compiler about "const" being discarded. The warning is correct: nvlist values are supposed to be immutable. However, fixing this properly will require some contortions on behalf of consumers who look up a subtree of the config and modify it. Per a discussion on freebsd-virtualization@, the solution will probably be to outright replace the use of nvlists for VM configuration, but until that happens let's document the problem and silence the warning. No functional change intended. MFC after: 2 weeks Reviewed by: corvink, jhb Differential Revision: https://reviews.freebsd.org/D37293 --- usr.sbin/bhyve/config.c | 16 +++++++++++++++- 1 file changed, 15 insertions(+), 1 deletion(-) diff --git a/usr.sbin/bhyve/config.c b/usr.sbin/bhyve/config.c index de138795f4d1..6339ddb9f2ee 100644 --- a/usr.sbin/bhyve/config.c +++ b/usr.sbin/bhyve/config.c @@ -65,7 +65,17 @@ _lookup_config_node(nvlist_t *parent, const char *path, bool create) break; } if (nvlist_exists_nvlist(nvl, name)) - nvl = (nvlist_t *)nvlist_get_nvlist(nvl, name); + /* + * XXX-MJ it is incorrect to cast away the const + * qualifier like this since the contract with nvlist + * says that values are immuatable, and some consumers + * will indeed add nodes to the returned nvlist. In + * practice, however, it appears to be harmless with the + * current nvlist implementation, so we just live with + * it until the implementation is reworked. + */ + nvl = __DECONST(nvlist_t *, + nvlist_get_nvlist(nvl, name)); else if (nvlist_exists(nvl, name)) { for (copy = tofree; copy < name; copy++) if (*copy == '\0') @@ -76,6 +86,10 @@ _lookup_config_node(nvlist_t *parent, const char *path, bool create) nvl = NULL; break; } else if (create) { + /* + * XXX-MJ as with the case above, "new_nvl" shouldn't be + * mutated after its ownership is given to "nvl". + */ new_nvl = nvlist_create(0); if (new_nvl == NULL) errx(4, "Failed to allocate memory");
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