ffi: pass non-empty slice when haystack is empty #43
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To work around likely bugs in (older versions of) PCRE2. Namely, at one point, PCRE2 would dereference the haystack pointer even when the length was zero. This was reported in #10 and we worked around this in #11 by passing a pointer to a const `&[]`, with the (erroneous) presumption that this would be a valid pointer to dereference. In retrospect though, this was a little silly, because you should never be dereferencing a pointer to an empty slice. It's not valid. Alas, at that time, Rust did actually hand you a valid pointer that could be dereferenced. But [this PR][rust-pull] changed that. And thus, we're back to where we started: handing buggy versions of PCRE2 a zero length haystack with a dangling pointer. So we fix this once and for all by passing a slice of length 1, but with a haystack length of 0, to the PCRE2 search routine when searching an empty haystack. This will guarantee the provision of a dereferencable pointer should PCRE2 decide to dereference it. Fixes #42 [rust-pull]: rust-lang/rust#123936
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To work around likely bugs in (older versions of) PCRE2. Namely, at one
point, PCRE2 would dereference the haystack pointer even when the length
was zero.
This was reported in #10 and we worked around this in #11 by passing a
pointer to a const
&[], with the (erroneous) presumption that thiswould be a valid pointer to dereference. In retrospect though, this was
a little silly, because you should never be dereferencing a pointer to
an empty slice. It's not valid. Alas, at that time, Rust did actually
hand you a valid pointer that could be dereferenced. But this
PR changed that. And thus, we're back to where we started:
handing buggy versions of PCRE2 a zero length haystack with a dangling
pointer.
So we fix this once and for all by passing a slice of length 1, but with
a haystack length of 0, to the PCRE2 search routine when searching an
empty haystack. This will guarantee the provision of a dereferencable
pointer should PCRE2 decide to dereference it.
Fixes #42