PPC: Detect unpooled string literal references #188
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encounter
approved these changes
Apr 17, 2025
| // Numeric type. | ||
| return Some(ty); | ||
| } | ||
| if bytes.len() >= 2 && bytes.iter().position(|&c| c == b'\0') == Some(bytes.len() - 1) { |
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| if bytes.len() >= 2 && bytes.iter().position(|&c| c == b'\0') == Some(bytes.len() - 1) { | |
| if bytes.len() >= 2 && bytes.iter().position(|&c| c == b'\0') == bytes.last() { |
I think this should work
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last would return the last byte in the slice, I think? This is comparing to the last index (len-1), not the value, since all the values were already read inside the loop.
The compiler also doesn't like last for some reason:
can't compare `std::option::Option<usize>` with `std::option::Option<&u8>`
the trait `PartialEq<std::option::Option<&u8>>` is not implemented for `std::option::Option<usize>`
but trait `PartialEq<deranged::OptionRangedUsize<_, _>>` is implemented for it
for that trait implementation, expected `deranged::OptionRangedUsize<_, _>`, found `std::option::Option<&u8>`
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I think my brain was melted by C++ iterators, nevermind
| return Some(ty); | ||
| } | ||
| if bytes.len() >= 2 && bytes.iter().position(|&c| c == b'\0') == Some(bytes.len() - 1) { | ||
| // It may be an unpooled string if the symbol contains exactly one null byte at the end of the symbol. |
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Doesn't have to be this PR, just thinking aloud, this logic could easily live in common arch code.
|
Thanks! |
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objdiff already supports detected pooled PPC strings (
@stringBase), this PR adds support for unpooled ones as well:It assumes that a data symbol is an unpooled string if it's at least 2 bytes long and it contains exactly 1 null byte at the end of the symbol. I didn't check that all the bytes are displayable ASCII characters because I didn't want to exclude non-ASCII strings. This might have false positives but I haven't run into any in testing yet.