error: attempt to dereference non-pointer type '?*. on generated cimport code

[brentp]

given this code for htslib

const std = @import("std");

const hts = @cImport({
    // htslib.org
    @cInclude("htslib/hts.h");
    @cInclude("htslib/sam.h");
});

pub fn main() !void {
    const stdout = std.io.getStdOut().writer();
    var v = hts.hts_version();
    try stdout.print("version, {s}!\n", .{v});

    var fh = hts.hts_open("/data/human/hg002.22.bam", "r");
    if (fh == null) {
        std.debug.warn("null file: {}", .{v});
    }
    try stdout.print("eof?:{d}\n", .{hts.hts_check_EOF(fh)});

    var hdr = hts.sam_hdr_read(fh);
    try stdout.print("null header?:{d}\n", .{hdr == null});

    var idx = hts.sam_index_load(fh, "/data/human/hg002.22.bam");
    try stdout.print("null idx?:{d}\n", .{idx == null});

    var qiter = hts.sam_itr_querys(idx, hdr, "22:450000");
    try stdout.print("null itr?:{d}\n", .{qiter == null});

    var b = hts.bam_init1();
    // ? https://github.com/ziglang/zig/issues/1580
    var ret = hts.sam_itr_next(fh, qiter, b);

    try stdout.print("next ret?:{d}\n", .{ret});
}

with this build.zig:

const Builder = @import("std").build.Builder;

pub fn build(b: *Builder) void {
    // Standard target options allows the person running `zig build` to choose
    // what target to build for. Here we do not override the defaults, which
    // means any target is allowed, and the default is native. Other options
    // for restricting supported target set are available.
    const target = b.standardTargetOptions(.{});

    // Standard release options allow the person running `zig build` to select
    // between Debug, ReleaseSafe, ReleaseFast, and ReleaseSmall.
    const mode = b.standardReleaseOptions();



    const exe = b.addExecutable("testing", "src/main.zig");
    exe.setTarget(target);
    exe.setBuildMode(mode);
    exe.linkSystemLibrary("c");
    exe.linkSystemLibrary("hts");
    exe.linkSystemLibrary("z");
    exe.install();

    const run_cmd = exe.run();
    run_cmd.step.dependOn(b.getInstallStep());

    const run_step = b.step("run", "Run the app");
    run_step.dependOn(&run_cmd.step);
}

I see:

$ zig build run
./zig-cache/o/dcfbafb6d0153b3f88717a785e6d092a/cimport.zig:863:16: error: attempt to dereference non-pointer type '?*.cimport:3:13.struct_unnamed_7'
    if (!(htsfp.*.is_bgzf != 0) and !(htsfp.*.is_cram != 0)) {
               ^
testing...The following command exited with error code 1:
/home/brentp/src/zig/zig-linux-x86_64-0.6.0+dbc11be03/zig build-exe /home/brentp/src/zig/zig-linux-x86_64-0.6.0+dbc11be03/t/src/main.zig --library c --library hts --library z --cache-dir /home/brentp/src/zig/zig-linux-x86_64-0.6.0+dbc11be03/t/zig-cache --name testing --enable-cache 
error: the following build command failed with exit code 1:
/home/brentp/src/zig/zig-linux-x86_64-0.6.0+dbc11be03/t/zig-cache/o/8e1f36000a4ecc95fc3c8c1975b6999b/build /home/brentp/src/zig/zig-linux-x86_64-0.6.0+dbc11be03/zig /home/brentp/src/zig/zig-linux-x86_64-0.6.0+dbc11be03/t /home/brentp/src/zig/zig-linux-x86_64-0.6.0+dbc11be03/t/zig-cache run

This happens only after I add the lines starting with: var ret = hts.sam_itr_next(fh, qiter, b);

There is a similar error reported in one of the comments in #1580

[brentp]

I think this happens when the struct is opaque, but then the header still accesses the fields. In this case, htsFile is opaque:

const struct_unnamed_7 = @Type(.Opaque); // /usr/local/include/htslib/hts.h:235:14: warning: struct demoted to opaque type - has bitfield
pub const htsFile = struct_unnamed_7;

but then the header still accesses fields within htsFile

[Vexu]

With #9100 the function with the dereference is should now be demoted to extern, bitfield support is tracked in #1499.