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This is an example of documentation generated by ZigDoc, an alternative to Zig's built-in Auto Doc feature. See also examples in other modes/formats. The project being documented here (as the example) is the Zig standard library. Public Function

lookupPc

Doc Source

Public Function

std.debug.Dwarf.Unwind.lookupPc

pub fn lookupPc(unwind: *const Unwind, pc: u64, addr_size_bytes: u8, endian: Endian) !?u64

Given a program counter value, returns the offset of the corresponding FDE, or null if no matching FDE was found. The returned offset can be passed to getFde to load the data associated with the FDE.

Before calling this function, prepare must return successfully at least once, to ensure that unwind.lookup is populated.

The return value may be a false positive. After loading the FDE with loadFde, the caller must validate that pc is indeed in its range -- if it is not, then no FDE matches pc.

Params

unwind: *const Unwind
pc: u64
addr_size_bytes: u8
endian: Endian

File

debug/Dwarf/Unwind.zig:583

pub fn lookupPc(unwind: *const Unwind, pc: u64, addr_size_bytes: u8, endian: Endian) !?u64 {
    const sorted_fdes: []const SortedFdeEntry = switch (unwind.lookup.?) {
        .eh_frame_hdr => |eh_frame_hdr| {
            const fde_vaddr = try eh_frame_hdr.table.findEntry(
                eh_frame_hdr.vaddr,
                pc,
                addr_size_bytes,
                endian,
            ) orelse return null;
            return std.math.sub(u64, fde_vaddr, unwind.frame_section.vaddr) catch bad(); // convert vaddr to offset
        },
        .sorted_fdes => |sorted_fdes| sorted_fdes,
    };
    if (sorted_fdes.len == 0) return null;
    var start: usize = 0;
    var len: usize = sorted_fdes.len;
    while (len > 1) {
        const half = len / 2;
        if (pc < sorted_fdes[start + half].pc_begin) {
            len = half;
        } else {
            start += half;
            len -= half;
        }
    }
    // If any FDE matches, it'll be the one at `start` (maybe false positive).
    return sorted_fdes[start].fde_offset;
}