[ruby-core:91129] [Ruby trunk Bug#15543] rb_str_set_len should clear code range

[ruby-core:91129] [Ruby trunk Bug#15543] rb_str_set_len should clear code range

[ruby]

Issue #15543 has been reported by nirvdrum (Kevin Menard).

----------------------------------------
Bug #15543: rb_str_set_len should clear code range
https://bugs.ruby-lang.org/issues/15543

* Author: nirvdrum (Kevin Menard)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.6.0p0 (2018-12-25 revision 66547) [x86_64-linux]
* Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN
----------------------------------------
Calling `rb_str_set_len` on a `String` could alter the code range. I think this hasn't been much of an issue because of pure luck rather than anything that was deliberately designed. If called on a string that already has a `CR_UNKNOWN` code range, there's no problem because the correct values will lazily calculated.

An example invocation that could be problematic, using helper methods for writing C API specs from the Ruby Spec Suite, looks like:

```
@str = "abcdefghij"[0..-1]
@s.rb_str_set_len(@str, 1)
@str.should == "a"

@str.force_encoding(Encoding::UTF_8)
@str.valid_encoding?.should == true
@s.RSTRING_PTR_set(@str, 1, 'B'.ord)
@s.RSTRING_PTR_set(@str, 2, 0x80)
@s.rb_str_set_len(@str, 3)

p @str
@str.valid_encoding?.should == false # This line fails because the cached code range hasn't been updated.

```

The first call to `valid_encoding?` forces the code range to be calculated for the string and it's determined to be `CR_7BIT`. Then `rb_str_set_len` is called, simulating the splitting the bytes of a valid UTF-8 multi-byte character. Here, the code range is still cached as `CR_7BIT`, but the byte sequence is invalid for UTF-8.

I think the fix is a simple matter of clearing the code range in `rb_str_set_len`, but I'd appreciate a review of my analysis.




-- 
https://bugs.ruby-lang.org/

[ruby-core:91133] [Ruby trunk Bug#15543] rb_str_set_len should clear code range

[nobu]

Issue #15543 has been updated by nobu (Nobuyoshi Nakada).

Status changed from Open to Rejected

It isn't an issue of `rb_str_set_len`.
The string isn't valid encoding by `@s.RSTRING_PTR_set(@str, 2, 0x80)`.
You should call `rb_str_modify` before modifying a string object.


----------------------------------------
Bug #15543: rb_str_set_len should clear code range
https://bugs.ruby-lang.org/issues/15543#change-76364

* Author: nirvdrum (Kevin Menard)
* Status: Rejected
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.6.0p0 (2018-12-25 revision 66547) [x86_64-linux]
* Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN
----------------------------------------
Calling `rb_str_set_len` on a `String` could alter the code range. I think this hasn't been much of an issue because of pure luck rather than anything that was deliberately designed. If called on a string that already has a `CR_UNKNOWN` code range, there's no problem because the correct values will lazily calculated.

An example invocation that could be problematic, using helper methods for writing C API specs from the Ruby Spec Suite, looks like:

```
@str = "abcdefghij"[0..-1]
@s.rb_str_set_len(@str, 1)
@str.should == "a"

@str.force_encoding(Encoding::UTF_8)
@str.valid_encoding?.should == true
@s.RSTRING_PTR_set(@str, 1, 'B'.ord)
@s.RSTRING_PTR_set(@str, 2, 0x80)
@s.rb_str_set_len(@str, 3)

p @str
@str.valid_encoding?.should == false # This line fails because the cached code range hasn't been updated.

```

The first call to `valid_encoding?` forces the code range to be calculated for the string and it's determined to be `CR_7BIT`. Then `rb_str_set_len` is called, simulating the splitting the bytes of a valid UTF-8 multi-byte character. Here, the code range is still cached as `CR_7BIT`, but the byte sequence is invalid for UTF-8.

I think the fix is a simple matter of clearing the code range in `rb_str_set_len`, but I'd appreciate a review of my analysis.




-- 
https://bugs.ruby-lang.org/

[ruby-core:91134] [Ruby trunk Bug#15543] rb_str_set_len should clear code range

[eregontp]

Issue #15543 has been updated by Eregon (Benoit Daloze).


I think few people know about this, and `rb_str_modify` isn't documented in doc/extension.rdoc.
I guess some C extensions ignore this requirement and could have bugs because of it.

Isn't it simpler and safer to clear the coderange, as it's done for, e.g., rb_str_resize() ?

----------------------------------------
Bug #15543: rb_str_set_len should clear code range
https://bugs.ruby-lang.org/issues/15543#change-76365

* Author: nirvdrum (Kevin Menard)
* Status: Rejected
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.6.0p0 (2018-12-25 revision 66547) [x86_64-linux]
* Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN
----------------------------------------
Calling `rb_str_set_len` on a `String` could alter the code range. I think this hasn't been much of an issue because of pure luck rather than anything that was deliberately designed. If called on a string that already has a `CR_UNKNOWN` code range, there's no problem because the correct values will lazily calculated.

An example invocation that could be problematic, using helper methods for writing C API specs from the Ruby Spec Suite, looks like:

```
@str = "abcdefghij"[0..-1]
@s.rb_str_set_len(@str, 1)
@str.should == "a"

@str.force_encoding(Encoding::UTF_8)
@str.valid_encoding?.should == true
@s.RSTRING_PTR_set(@str, 1, 'B'.ord)
@s.RSTRING_PTR_set(@str, 2, 0x80)
@s.rb_str_set_len(@str, 3)

p @str
@str.valid_encoding?.should == false # This line fails because the cached code range hasn't been updated.

```

The first call to `valid_encoding?` forces the code range to be calculated for the string and it's determined to be `CR_7BIT`. Then `rb_str_set_len` is called, simulating the splitting the bytes of a valid UTF-8 multi-byte character. Here, the code range is still cached as `CR_7BIT`, but the byte sequence is invalid for UTF-8.

I think the fix is a simple matter of clearing the code range in `rb_str_set_len`, but I'd appreciate a review of my analysis.




-- 
https://bugs.ruby-lang.org/

[ruby-core:91157] [Ruby trunk Bug#15543] rb_str_set_len should clear code range

[nobu]

Issue #15543 has been updated by nobu (Nobuyoshi Nakada).


`rb_str_set_len` is not the true problem.
Should `RSTRING_PTR` make the object unshared and clear the code range?
Or enclose it only for the core and prohibit in extension libraries?

Hmmm, the last choice may be the best, I think.

----------------------------------------
Bug #15543: rb_str_set_len should clear code range
https://bugs.ruby-lang.org/issues/15543#change-76388

* Author: nirvdrum (Kevin Menard)
* Status: Rejected
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.6.0p0 (2018-12-25 revision 66547) [x86_64-linux]
* Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN
----------------------------------------
Calling `rb_str_set_len` on a `String` could alter the code range. I think this hasn't been much of an issue because of pure luck rather than anything that was deliberately designed. If called on a string that already has a `CR_UNKNOWN` code range, there's no problem because the correct values will lazily calculated.

An example invocation that could be problematic, using helper methods for writing C API specs from the Ruby Spec Suite, looks like:

```
@str = "abcdefghij"[0..-1]
@s.rb_str_set_len(@str, 1)
@str.should == "a"

@str.force_encoding(Encoding::UTF_8)
@str.valid_encoding?.should == true
@s.RSTRING_PTR_set(@str, 1, 'B'.ord)
@s.RSTRING_PTR_set(@str, 2, 0x80)
@s.rb_str_set_len(@str, 3)

p @str
@str.valid_encoding?.should == false # This line fails because the cached code range hasn't been updated.

```

The first call to `valid_encoding?` forces the code range to be calculated for the string and it's determined to be `CR_7BIT`. Then `rb_str_set_len` is called, simulating the splitting the bytes of a valid UTF-8 multi-byte character. Here, the code range is still cached as `CR_7BIT`, but the byte sequence is invalid for UTF-8.

I think the fix is a simple matter of clearing the code range in `rb_str_set_len`, but I'd appreciate a review of my analysis.




-- 
https://bugs.ruby-lang.org/

[ruby-core:91193] [Ruby trunk Bug#15543] rb_str_set_len should clear code range

[eregontp]

Issue #15543 has been updated by Eregon (Benoit Daloze).


nobu (Nobuyoshi Nakada) wrote:
> `rb_str_set_len` is not the true problem.
> Should `RSTRING_PTR` make the object unshared and clear the code range?

That sounds safer, because indeed as soon as the C code can access the `char*` it can change it.

> Or enclose it only for the core and prohibit in extension libraries?

I'm not sure what you mean?

Do you mean removing rb_str_set_len() or RSTRING_PTR from the public C-API?
Or do you mean in core, a special version of RSTRING_PTR would be used?
Or something else?

----------------------------------------
Bug #15543: rb_str_set_len should clear code range
https://bugs.ruby-lang.org/issues/15543#change-76425

* Author: nirvdrum (Kevin Menard)
* Status: Rejected
* Priority: Normal
* Assignee: 
* Target version: 
* ruby -v: ruby 2.6.0p0 (2018-12-25 revision 66547) [x86_64-linux]
* Backport: 2.4: UNKNOWN, 2.5: UNKNOWN, 2.6: UNKNOWN
----------------------------------------
Calling `rb_str_set_len` on a `String` could alter the code range. I think this hasn't been much of an issue because of pure luck rather than anything that was deliberately designed. If called on a string that already has a `CR_UNKNOWN` code range, there's no problem because the correct values will lazily calculated.

An example invocation that could be problematic, using helper methods for writing C API specs from the Ruby Spec Suite, looks like:

```
@str = "abcdefghij"[0..-1]
@s.rb_str_set_len(@str, 1)
@str.should == "a"

@str.force_encoding(Encoding::UTF_8)
@str.valid_encoding?.should == true
@s.RSTRING_PTR_set(@str, 1, 'B'.ord)
@s.RSTRING_PTR_set(@str, 2, 0x80)
@s.rb_str_set_len(@str, 3)

p @str
@str.valid_encoding?.should == false # This line fails because the cached code range hasn't been updated.

```

The first call to `valid_encoding?` forces the code range to be calculated for the string and it's determined to be `CR_7BIT`. Then `rb_str_set_len` is called, simulating the splitting the bytes of a valid UTF-8 multi-byte character. Here, the code range is still cached as `CR_7BIT`, but the byte sequence is invalid for UTF-8.

I think the fix is a simple matter of clearing the code range in `rb_str_set_len`, but I'd appreciate a review of my analysis.




-- 
https://bugs.ruby-lang.org/