diff --git a/lib/libc/glibc/csu/init.c b/lib/libc/glibc/csu/init.c new file mode 100644 index 0000000000..3ee6148898 --- /dev/null +++ b/lib/libc/glibc/csu/init.c @@ -0,0 +1,23 @@ +/* Special startup support. + Copyright (C) 1997-2024 Free Software Foundation, Inc. + This file is part of the GNU C Library. + + The GNU C Library is free software; you can redistribute it and/or + modify it under the terms of the GNU Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + The GNU C Library is distributed in the hope that it will be useful, + but WITHOUT ANY WARRANTY; without even the implied warranty of + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library; if not, see + . */ + +/* Vestigial libio version number. Some code in libio checks whether + this symbol exists in the executable, but nothing looks at its + value anymore; the value it was historically set to has been + preserved out of an abundance of caution. */ +const int _IO_stdin_used = 0x20001; diff --git a/src/glibc.zig b/src/glibc.zig index 57894f5921..4689805391 100644 --- a/src/glibc.zig +++ b/src/glibc.zig @@ -286,7 +286,11 @@ pub fn buildCRTFile(comp: *Compilation, crt_file: CRTFile, prog_node: std.Progre .owner = undefined, }; }; - var files = [_]Compilation.CSourceFile{ start_o, abi_note_o }; + const init_o: Compilation.CSourceFile = .{ + .src_path = try lib_path(comp, arena, lib_libc_glibc ++ "csu" ++ path.sep_str ++ "init.c"), + .owner = undefined, + }; + var files = [_]Compilation.CSourceFile{ start_o, abi_note_o, init_o }; return comp.build_crt_file("Scrt1", .Obj, .@"glibc Scrt1.o", prog_node, &files); }, .libc_nonshared_a => { @@ -682,6 +686,12 @@ pub const BuiltSharedObjects = struct { const all_map_basename = "all.map"; +fn wordDirective(target: std.Target) []const u8 { + // Based on its description in the GNU `as` manual, you might assume that `.word` is sized + // according to the target word size. But no; that would just make too much sense. + return if (target.ptrBitWidth() == 64) ".quad" else ".long"; +} + pub fn buildSharedObjects(comp: *Compilation, prog_node: std.Progress.Node) !void { const tracy = trace(@src()); defer tracy.end(); @@ -923,6 +933,31 @@ pub fn buildSharedObjects(comp: *Compilation, prog_node: std.Progress.Node) !voi try stubs_asm.appendSlice(".data\n"); + // For some targets, the real `libc.so.6` will contain a weak reference to `_IO_stdin_used`, + // making the linker put the symbol in the dynamic symbol table. We likewise need to emit a + // reference to it here for that effect, or it will not show up, which in turn will cause + // the real glibc to think that the program was built against an ancient `FILE` structure + // (pre-glibc 2.1). + // + // Note that glibc only compiles in the legacy compatibility code for some targets; it + // depends on what is defined in the `shlib-versions` file for the particular architecture + // and ABI. Those files are preprocessed by 2 separate tools during the glibc build to get + // the final `abi-versions.h`, so it would be quite brittle to try to condition our emission + // of the `_IO_stdin_used` reference in the exact same way. The only downside of emitting + // the reference unconditionally is that it ends up being unused for newer targets; it + // otherwise has no negative effect. + // + // glibc uses a weak reference because it has to work with programs compiled against pre-2.1 + // versions where the symbol didn't exist. We only care about modern glibc versions, so use + // a strong reference. + if (std.mem.eql(u8, lib.name, "c")) { + try stubs_asm.writer().print( + \\.globl _IO_stdin_used + \\{s} _IO_stdin_used + \\ + , .{wordDirective(target)}); + } + const obj_inclusions_len = mem.readInt(u16, metadata.inclusions[inc_i..][0..2], .little); inc_i += 2;