From ee87f50b8d2a0599675657a9fd2774c08261b29c Mon Sep 17 00:00:00 2001 From: Nick Alcock Date: Fri, 29 Jan 2021 13:33:11 +0000 Subject: libctf: always name nameless types "", never NULL The ctf_type_name_raw and ctf_type_aname_raw functions, which return the raw, unadorned name of CTF types, have one unfortunate wrinkle: they return NULL not only on error but when returning the name of types without a name in writable dicts. This was unintended: it not only makes it impossible to reliably tell if a given call to ctf_type_name_raw failed (due to a bad string offset say), but also complicates all its callers, who now have to check for both NULL and "". The written-out form of CTF has no concept of a NULL pointer instead of a string: all null strings are strtab offset 0, "". So the more we can do to remove this distinction from the writable form, the less complex the rest of our code needs to be. Armour against NULL in multiple places, arranging to return "" from ctf_type_name_raw if offset 0 is passed in, and removing a risky optimization from ctf_str_add* that avoided doing anything if a NULL was passed in: this added needless irregularity to the functions' API surface, since "" and NULL should be treated identically, and in the case of ctf_str_add_ref, we shouldn't skip adding the passed-in REF to the list of references to be updated no matter what the content of the string happens to be. This means we can simplify the deduplicator a tiny bit, also fixing a bug (latent when used by ld) where if the input dict was writable, we failed to realise when types were nameless and could end up creating deeply unhelpful synthetic forwards with no name, which we just banned a few commits ago, so the link failed. libctf/ChangeLog 2021-01-27 Nick Alcock * ctf-string.c (ctf_str_add): Treat adding a NULL as adding "". (ctf_str_add_ref): Likewise. (ctf_str_add_external): Likewise. * ctf-types.c (ctf_type_name_raw): Always return "" for offset 0. * ctf-dedup.c (ctf_dedup_multiple_input_dicts): Don't armour against NULL name. (ctf_dedup_maybe_synthesize_forward): Likewise. --- libctf/ChangeLog | 10 ++++++++++ libctf/ctf-dedup.c | 7 +++---- libctf/ctf-string.c | 9 ++++++--- libctf/ctf-types.c | 8 +++++++- 4 files changed, 26 insertions(+), 8 deletions(-) (limited to 'libctf') diff --git a/libctf/ChangeLog b/libctf/ChangeLog index c700297..35c22d9 100644 --- a/libctf/ChangeLog +++ b/libctf/ChangeLog @@ -1,5 +1,15 @@ 2021-01-27 Nick Alcock + * ctf-string.c (ctf_str_add): Treat adding a NULL as adding "". + (ctf_str_add_ref): Likewise. + (ctf_str_add_external): Likewise. + * ctf-types.c (ctf_type_name_raw): Always return "" for offset 0. + * ctf-dedup.c (ctf_dedup_multiple_input_dicts): Don't armour + against NULL name. + (ctf_dedup_maybe_synthesize_forward): Likewise. + +2021-01-27 Nick Alcock + * ctf-create.c (ctf_serialize): Fix shadowing. 2021-01-27 Nick Alcock diff --git a/libctf/ctf-dedup.c b/libctf/ctf-dedup.c index da88ae371..001c248 100644 --- a/libctf/ctf-dedup.c +++ b/libctf/ctf-dedup.c @@ -1776,7 +1776,7 @@ ctf_dedup_multiple_input_dicts (ctf_dict_t *output, ctf_dict_t **inputs, name = ctf_type_name_raw (input_fp, input_id); if ((fwdkind == CTF_K_STRUCT || fwdkind == CTF_K_UNION) - && name && name[0] != '\0') + && name[0] != '\0') { const void *origin; @@ -2375,20 +2375,19 @@ ctf_dedup_maybe_synthesize_forward (ctf_dict_t *output, ctf_dict_t *target, ctf_dedup_t *td = &target->ctf_dedup; int kind; int fwdkind; - const char *name; + const char *name = ctf_type_name_raw (input, id); const char *decorated; void *v; ctf_id_t emitted_forward; if (!ctf_dynset_exists (od->cd_conflicting_types, hval, NULL) || target->ctf_flags & LCTF_CHILD - || !ctf_type_name_raw (input, id) + || name[0] == '\0' || (((kind = ctf_type_kind_unsliced (input, id)) != CTF_K_STRUCT && kind != CTF_K_UNION && kind != CTF_K_FORWARD))) return 0; fwdkind = ctf_type_kind_forwarded (input, id); - name = ctf_type_name_raw (input, id); ctf_dprintf ("Using synthetic forward for conflicted struct/union with " "hval %s\n", hval); diff --git a/libctf/ctf-string.c b/libctf/ctf-string.c index cb36f91..91ad2e3 100644 --- a/libctf/ctf-string.c +++ b/libctf/ctf-string.c @@ -218,8 +218,9 @@ uint32_t ctf_str_add (ctf_dict_t *fp, const char *str) { ctf_str_atom_t *atom; + if (!str) - return 0; + str = ""; atom = ctf_str_add_ref_internal (fp, str, FALSE, TRUE, 0); if (!atom) @@ -235,8 +236,9 @@ uint32_t ctf_str_add_ref (ctf_dict_t *fp, const char *str, uint32_t *ref) { ctf_str_atom_t *atom; + if (!str) - return 0; + str = ""; atom = ctf_str_add_ref_internal (fp, str, TRUE, TRUE, ref); if (!atom) @@ -251,8 +253,9 @@ int ctf_str_add_external (ctf_dict_t *fp, const char *str, uint32_t offset) { ctf_str_atom_t *atom; + if (!str) - return 0; + str = ""; atom = ctf_str_add_ref_internal (fp, str, FALSE, FALSE, 0); if (!atom) diff --git a/libctf/ctf-types.c b/libctf/ctf-types.c index 4129fbc..57a284d 100644 --- a/libctf/ctf-types.c +++ b/libctf/ctf-types.c @@ -922,7 +922,10 @@ ctf_type_name (ctf_dict_t *fp, ctf_id_t type, char *buf, size_t len) } /* Lookup the given type ID and return its raw, unadorned, undecorated name. - The name will live as long as its ctf_dict_t does. */ + The name will live as long as its ctf_dict_t does. + + The only decoration is that a NULL return always means an error: nameless + types return a null string. */ const char * ctf_type_name_raw (ctf_dict_t *fp, ctf_id_t type) @@ -932,6 +935,9 @@ ctf_type_name_raw (ctf_dict_t *fp, ctf_id_t type) if ((tp = ctf_lookup_by_id (&fp, type)) == NULL) return NULL; /* errno is set for us. */ + if (tp->ctt_name == 0) + return ""; + return ctf_strraw (fp, tp->ctt_name); } -- cgit v1.1