Constant wasmtime_environ::ELF_WASMTIME_TRAPS

pub const ELF_WASMTIME_TRAPS: &str = ".wasmtime.traps";

A custom binary-encoded section of wasmtime compilation artifacts which encodes the ability to map an offset in the text section to the trap code that it corresponds to.

This section is used at runtime to determine what flavor fo trap happened to ensure that embedders and debuggers know the reason for the wasm trap. The encoding of this section is custom to Wasmtime and managed with helpers in the object crate:

• First the section has a 32-bit little endian integer indicating how many trap entries are in the section.
• Next is an array, of the same length as read before, of 32-bit little-endian integers. These integers are offsets into the text section of the compilation image.
• Finally is the same count number of bytes. Each of these bytes corresponds to a trap code.

This section is decoded by lookup_trap_code below which will read the section count, slice some bytes to get the various arrays, and then perform a binary search on the offsets array to find the an index corresponding to the pc being looked up. If found the same index in the trap array (the array of bytes) is the trap code for that offset.

Note that at this time this section has an alignment of 1. Additionally due to the 32-bit encodings for offsets this doesn’t support images >=4gb.