Unicode security

[Joseph Myers]

On Mon, 10 Jan 2022, Paul Koning via Binutils wrote:

> A standard that needs to handle Unicode and have a definition of "equal 
> strings" will want to refer to a particular normalization.

For the purposes of ELF, equal strings are equal octet sequences, with no 
further interpretation.

The ELF bindings to C do not need a concept of "equal", they just need to 
say that UTF-8 is used to encode the sequence of Unicode code points in 
the C symbol.  Those bindings need to handle multiple C versions with 
different sets of allowed characters in identifiers, some of which allow 
identifiers that are different as sequences of Unicode code points, and 
thus different in C and in UTF-8, although the same in NFC.  In those 
cases, the bindings need to result in different octet sequences in ELF 
symbols for those different (but normalized the same) C identifiers.  When 
a C identifier is written in NFC, so must the ELF symbol be; when a C 
identifier is written in NFD, so must the ELF symbol be; when a C 
identifier is in neither normalization form, so must the ELF symbol be.

-- 
Joseph S. Myers
joseph@codesourcery.com