Missing BN_* prefixed symbols and library in output binary when dynamic linking

[bullekeup]

Zig Version

0.16.0-dev.1364+f0a3df98d

Steps to Reproduce and Observed Behavior

When dynamically linking system provided OpenSSL with 0.16.0-dev.1364+f0a3df98d, every symbol that starts with BN_* is stripped out of the output binary, nothing shown with readelf -s.

If only BN_* functions are used libcrypto is not linked at all (not shown in ldd output).

This only affects BN_* prefixed OpenSSL symbols, if used, other symbols (X509, ...) are present and properly linked. Something related to the BN_* name that triggers a specific behaviour at build / link time maybe ? I looked through the code but failed to find anything relevant.

I tried to link with lld, it fails to link and crash.

Building with LLVM also fails with the following linkage issue:

error: Global is external, but doesn't have external or weak linkage!
       ptr @openssl_bn.main
       LLVM ERROR: Broken module found, compilation aborted!

Sample code :

// openssl_bn.zig
const std = @import("std");

pub const log_level = std.log.Level.debug;

pub const c = @cImport({
    @cInclude("openssl/bn.h");
});

pub fn main() void {
    std.log.info("*Start test*", .{});

    const value: ?*c.BIGNUM = c.BN_new() orelse {
        std.log.err("Failed to create BN", .{});
        return;
    };
    defer c.BN_free(value);
    _ = c.BN_set_word(value, 1);
    std.log.debug("value: {d}", .{c.BN_get_word(value)});
}

Interestingly, building a small test.c file with zig cc works properly

// zig cc -lc -lcrypto test.c -o test
#include <openssl/bn.h>
#include <stdio.h>

int main() {
  BIGNUM *bn = BN_new();
  BN_set_word(bn, 1);
  printf("%lu\n", BN_get_word(bn));
  BN_free(bn);
  return 0;
}

Reproduced on Ubuntu 25.10 x86_64 and Fedora 43 aarch64

Note: building with zig 0.15.2 works as expected, BN_* symbols are present in the binary.

I made a small repo to reproduce easily at https://github.com/bullekeup/zig-issue-openssl.git

Expected Behavior

Symbols present in the binary as reported by readelf :

readelf -s ./zig-out/bin/bn | grep BN_
  3539: 000000000101a220    16 FUNC    LOCAL  DEFAULT   17 BN_set_word$plt
  3540: 000000000101a230    16 FUNC    LOCAL  DEFAULT   17 BN_new$plt
  3541: 000000000101a240    16 FUNC    LOCAL  DEFAULT   17 BN_get_word$plt
  3542: 000000000101a250    16 FUNC    LOCAL  DEFAULT   17 BN_free$plt
  3575: 0000000000000000   103 FUNC    GLOBAL DEFAULT  UND BN_set_word
  3576: 0000000000000000    50 FUNC    GLOBAL DEFAULT  UND BN_new
  3577: 0000000000000000    41 FUNC    GLOBAL DEFAULT  UND BN_get_word
  3578: 0000000000000000   129 FUNC    GLOBAL DEFAULT  UND BN_free

[alexrp]

Is this a translate-c bug? cc @Vexu

[Vexu]

There was a bug in translate-c that caused duplicate opaque member name errors which are not reported when using @cImport but even with that fixed there seems to still be some issue with @cImport:

error(link): NAV a.main(1001) assigned symbol 2241 but not allocated!
Compiler crash context:
(no context)

thread 12665 panic: reached unreachable code
/home/vexu/.config/Code - OSS/User/globalStorage/ziglang.vscode-zig/zig/x86_64-linux-0.16.0-dev.1334+06d08daba/lib/std/debug.zig:416:14: 0x1b41089 in assert (std.zig)
    if (!ok) unreachable; // assertion failure
             ^
/home/vexu/Documents/zig/zig/src/link/Elf/ZigObject.zig:845:15: 0x2435338 in updateSymtabSize (main.zig)
        assert(name.len > 0);
              ^
/home/vexu/Documents/zig/zig/src/link/Elf/file.zig:222:50: 0x24364bd in updateSymtabSize (main.zig)
            inline else => |x| x.updateSymtabSize(elf_file),
                                                 ^
/home/vexu/Documents/zig/zig/src/link/Elf.zig:3084:38: 0x243706b in updateSymtabSize (main.zig)
        try file_ptr.updateSymtabSize(self);
                                     ^
/home/vexu/Documents/zig/zig/src/link/Elf.zig:2662:30: 0x243a4e3 in updateSectionSizes (main.zig)
    try self.updateSymtabSize();
                             ^
/home/vexu/Documents/zig/zig/src/link/Elf.zig:853:32: 0x2483a3a in flushInner (main.zig)
    try self.updateSectionSizes();
                               ^
/home/vexu/Documents/zig/zig/src/link/Elf.zig:756:22: 0x24869af in flush (main.zig)
    return flushInner(self, arena, tid) catch |err| switch (err) {
                     ^
/home/vexu/Documents/zig/zig/src/link.zig:929:77: 0x21424d2 in flush (main.zig)
                return @as(*tag.Type(), @fieldParentPtr("base", base)).flush(arena, tid, prog_node);
                                                                            ^
/home/vexu/Documents/zig/zig/src/Compilation.zig:3350:17: 0x1f8063f in flush (main.zig)
        lf.flush(arena, tid, comp.link_prog_node) catch |err| switch (err) {
                ^
/home/vexu/Documents/zig/zig/src/Compilation.zig:3197:22: 0x1e72a70 in update (main.zig)
            try flush(comp, arena, .main);
                     ^
/home/vexu/Documents/zig/zig/src/main.zig:4534:20: 0x1e800cb in updateModule (main.zig)
    try comp.update(prog_node);
                   ^

If you translate first and @import that then it works as expected.

[Vexu]

I can't reproduce whatever I was running into yesterday and #25780 fixed the original issue.