Re: [PATCH] apply: Avoid ambiguous pointer provenance for CHERI/Arm's Morello
From: Junio C Hamano <hidden>
Date: 2022-01-07 19:40:12
René Scharfe [off-list ref] writes:
quoted
I actually wonder if it results in code that is much easier to follow if we did: * Introduce an "enum apply_symlink_treatment" that has APPLY_SYMLINK_GOES_AWAY and APPLY_SYMLINK_IN_RESULT as its possible values; * Make register_symlink_changes() and check_symlink_changes() work with "enum apply_symlink_treatment"; * (optional) stop using string_list() to store the symlink_changes; use strintmap and use strintmap_set() and strintmap_get() to access its entries, so that the ugly implementation detail (i.e. "the container type we use only has a (void *) field to store caller-supplied data, so we cast an integer and a pointer back and forth") can be safely hidden.Or strsets -- we only need two.
True. When we check a path, we make a single look-up of two bit in a single hashtable but now we need two look-ups, but addition, removal and renaming of a symlink would be rare enough to matter either way. Will queue; thanks.
quoted hunk
--- >8 ---Subject: [PATCH] apply: use strsets to track symlinks Symlink changes are tracked in a string_list, with the util pointer value indicating whether a symlink is kept or removed. Using fake pointer values requires awkward casts. Use one strset for each type of change instead to simplify and shorten the code. Original-patch-by: Jessica Clarke [off-list ref] Signed-off-by: René Scharfe <redacted> --- apply.c | 42 ++++++++---------------------------------- apply.h | 26 +++++++++++--------------- 2 files changed, 19 insertions(+), 49 deletions(-)diff --git a/apply.c b/apply.c index fed195250b..7deb4f79fd 100644 --- a/apply.c +++ b/apply.c@@ -103,7 +103,8 @@ int init_apply_state(struct apply_state *state, state->linenr = 1; string_list_init_nodup(&state->fn_table); string_list_init_nodup(&state->limit_by_name); - string_list_init_nodup(&state->symlink_changes); + strset_init(&state->removed_symlinks); + strset_init(&state->kept_symlinks); strbuf_init(&state->root, 0); git_apply_config();@@ -117,7 +118,8 @@ int init_apply_state(struct apply_state *state, void clear_apply_state(struct apply_state *state) { string_list_clear(&state->limit_by_name, 0); - string_list_clear(&state->symlink_changes, 0); + strset_clear(&state->removed_symlinks); + strset_clear(&state->kept_symlinks); strbuf_release(&state->root); /* &state->fn_table is cleared at the end of apply_patch() */@@ -3812,59 +3814,31 @@ static int check_to_create(struct apply_state *state, return 0; } -static uintptr_t register_symlink_changes(struct apply_state *state, - const char *path, - uintptr_t what) -{ - struct string_list_item *ent; - - ent = string_list_lookup(&state->symlink_changes, path); - if (!ent) { - ent = string_list_insert(&state->symlink_changes, path); - ent->util = (void *)0; - } - ent->util = (void *)(what | ((uintptr_t)ent->util)); - return (uintptr_t)ent->util; -} - -static uintptr_t check_symlink_changes(struct apply_state *state, const char *path) -{ - struct string_list_item *ent; - - ent = string_list_lookup(&state->symlink_changes, path); - if (!ent) - return 0; - return (uintptr_t)ent->util; -} - static void prepare_symlink_changes(struct apply_state *state, struct patch *patch) { for ( ; patch; patch = patch->next) { if ((patch->old_name && S_ISLNK(patch->old_mode)) && (patch->is_rename || patch->is_delete)) /* the symlink at patch->old_name is removed */ - register_symlink_changes(state, patch->old_name, APPLY_SYMLINK_GOES_AWAY); + strset_add(&state->removed_symlinks, patch->old_name); if (patch->new_name && S_ISLNK(patch->new_mode)) /* the symlink at patch->new_name is created or remains */ - register_symlink_changes(state, patch->new_name, APPLY_SYMLINK_IN_RESULT); + strset_add(&state->kept_symlinks, patch->new_name); } } static int path_is_beyond_symlink_1(struct apply_state *state, struct strbuf *name) { do { - unsigned int change; - while (--name->len && name->buf[name->len] != '/') ; /* scan backwards */ if (!name->len) break; name->buf[name->len] = '\0'; - change = check_symlink_changes(state, name->buf); - if (change & APPLY_SYMLINK_IN_RESULT) + if (strset_contains(&state->kept_symlinks, name->buf)) return 1; - if (change & APPLY_SYMLINK_GOES_AWAY) + if (strset_contains(&state->removed_symlinks, name->buf)) /* * This cannot be "return 0", because we may * see a new one created at a higher level.diff --git a/apply.h b/apply.h index 16202da160..4052da50c0 100644 --- a/apply.h +++ b/apply.h@@ -4,6 +4,7 @@ #include "hash.h" #include "lockfile.h" #include "string-list.h" +#include "strmap.h" struct repository;@@ -25,20 +26,6 @@ enum apply_verbosity { verbosity_verbose = 1 }; -/* - * We need to keep track of how symlinks in the preimage are - * manipulated by the patches. A patch to add a/b/c where a/b - * is a symlink should not be allowed to affect the directory - * the symlink points at, but if the same patch removes a/b, - * it is perfectly fine, as the patch removes a/b to make room - * to create a directory a/b so that a/b/c can be created. - * - * See also "struct string_list symlink_changes" in "struct - * apply_state". - */ -#define APPLY_SYMLINK_GOES_AWAY 01 -#define APPLY_SYMLINK_IN_RESULT 02 - struct apply_state { const char *prefix;@@ -86,7 +73,16 @@ struct apply_state { /* Various "current state" */ int linenr; /* current line number */ - struct string_list symlink_changes; /* we have to track symlinks */ + /* + * We need to keep track of how symlinks in the preimage are + * manipulated by the patches. A patch to add a/b/c where a/b + * is a symlink should not be allowed to affect the directory + * the symlink points at, but if the same patch removes a/b, + * it is perfectly fine, as the patch removes a/b to make room + * to create a directory a/b so that a/b/c can be created. + */ + struct strset removed_symlinks; + struct strset kept_symlinks; /* * For "diff-stat" like behaviour, we keep track of the biggest change --2.34.1