Nick Alcock 6bd2318f32 libctf: fix linking together multiple objects derived from the same source ... Right now, if you compile the same .c input repeatedly with CTF enabled and different compilation flags, then arrange to link all of these together, then things misbehave in various ways. libctf may conflate either inputs (if the .o files have the same name, say if they are stored in different .a archives), or per-CU outputs when conflicting types are found: the latter can lead to entirely spurious errors when it tries to produce multiple per-CU outputs with the same name (discarding all but the last, but then looking for types in the earlier ones which have just been thrown away). Fixing this is multi-pronged. Both inputs and outputs need to be differentiated in the hashtables libctf keeps them in: inputs with the same cuname and filename need to be considered distinct as long as they have different associated CTF dicts, and per-CU outputs need to be considered distinct as long as they have different associated input dicts. Right now there is nothing tying the two together other than the CU name: fix this by introducing a new field in the ctf_dict_t named ctf_link_in_out, which (for input dicts) points to the associated per-CU output dict (if any), and for output dicts points to the associated input dict. At creation time the name used is completely arbitrary: it's only important that it be distinct if CTF dicts are distinct. So, when a clash is found, adjust the CU name by sticking the number of elements in the input on the end. At output time, the CU name will appear in the linked object, so it matters a little more that it look slightly less ugly: in conflicting cases, append an incrementing integer, starting at 0. This naming scheme is not very helpful, but it's hard to see what else we can do. The input .o name may be the same. The input .a name is not even visible to ctf_link, and even *that* might be the same, because .a's can contain many members with the same name, all of which participate in the link. All we really know is that the two have distinct dictionaries with distinct types in them, and at least this way they are all represented, any any symbols, variables etc referring to those types are accurately stored. (As a side-effect this also fixes a use-after-free and double-free when errors are found during variable or symbol emission.) Use the opportunity to prevent a couple of sources of problems, to wit changing the active CU mappings when a link has already been done (no effect on ld, which doesn't use CU mappings at all), and causing multiple consecutive ctf_link's to have the same net effect as just doing the last one (no effect on ld, which only ever does one ctf_link) rather than having the links be a sort of half-incremental not-really-intended mess. libctf/ChangeLog: PR libctf/29242 * ctf-impl.h (struct ctf_dict) [ctf_link_in_out]: New. * ctf-dedup.c (ctf_dedup_emit_type): Set it. * ctf-link.c (ctf_link_add_ctf_internal): Set the input CU name uniquely when clashes are found. (ctf_link_add): Document what repeated additions do. (ctf_new_per_cu_name): New, come up with a consistent name for a new per-CU dict. (ctf_link_deduplicating): Use it. (ctf_create_per_cu): Use it, and ctf_link_in_out, and set ctf_link_in_out properly. Don't overwrite per-CU dicts with per-CU dicts relating to different inputs. (ctf_link_add_cu_mapping): Prevent per-CU mappings being set up if we already have per-CU outputs. (ctf_link_one_variable): Adjust ctf_link_per_cu call. (ctf_link_deduplicating_one_symtypetab): Likewise. (ctf_link_empty_outputs): New, delete all the ctf_link_outputs and blank out ctf_link_in_out on the corresponding inputs. (ctf_link): Clarify the effect of multiple ctf_link calls. Empty ctf_link_outputs if it already exists rather than having the old output leak into the new link. Fix a variable name. * testsuite/config/default.exp (AR): Add. (OBJDUMP): Likewise. * testsuite/libctf-regression/libctf-repeat-cu.exp: New test. * testsuite/libctf-regression/libctf-repeat-cu*: Main program, library, and expected results for the test.		2022-06-21 19:27:15 +01:00
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default.exp	libctf: fix linking together multiple objects derived from the same source	2022-06-21 19:27:15 +01:00