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tag: avoid NULL pointer arithmetic

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lookup_blob() etc. can return NULL if the referenced object isn't of the
expected type.  In theory it's wrong to reference the object member in
that case.  In practice it's OK because it's located at offset 0 for all
types, so the pointer arithmetic (NULL + 0) is optimized out by the
compiler.  The issue is reported by Clang's AddressSanitizer, though.

Avoid the ASan error by casting the results of the lookup functions to
struct object pointers.  That works fine with NULL pointers as well.  We
already rely on the object member being first in all object types in
other places in the code.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
René Scharfe 2017-10-01 16:45:13 +02:00 committed by Junio C Hamano
parent 4010f1d1b7
commit 7099153e8d
1 changed files with 4 additions and 4 deletions
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8
tag.c
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@ -142,13 +142,13 @@ int parse_tag_buffer(struct tag *item, const void *data, unsigned long size)
bufptr = nl + 1;
if (!strcmp(type, blob_type)) {
item->tagged = &lookup_blob(&oid)->object;
item->tagged = (struct object *)lookup_blob(&oid);
} else if (!strcmp(type, tree_type)) {
item->tagged = &lookup_tree(&oid)->object;
item->tagged = (struct object *)lookup_tree(&oid);
} else if (!strcmp(type, commit_type)) {
item->tagged = &lookup_commit(&oid)->object;
item->tagged = (struct object *)lookup_commit(&oid);
} else if (!strcmp(type, tag_type)) {
item->tagged = &lookup_tag(&oid)->object;
item->tagged = (struct object *)lookup_tag(&oid);
} else {
error("Unknown type %s", type);
item->tagged = NULL;