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Report all undefined symbols correctly
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Previously, we failed to report an undefined error if we have two
undefined symbols, a strong and a weak one, for the same symbol.

It is an undefined symbol error if an undefined symbol is resolved
to a weak undefined symbol.

Fixes #967
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@rui314
rui314 committed Jan 18, 2023
1 parent 00af084 commit 8936194
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Showing 18 changed files with 119 additions and 85 deletions.
6 changes: 4 additions & 2 deletions elf/arch-alpha.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -170,9 +170,10 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = base + rel.r_offset;

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down Expand Up @@ -217,8 +218,9 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down
6 changes: 4 additions & 2 deletions elf/arch-arm32.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -506,9 +506,10 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = base + rel.r_offset;

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down Expand Up @@ -555,8 +556,9 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down
6 changes: 4 additions & 2 deletions elf/arch-arm64.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -413,9 +413,10 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = base + rel.r_offset;

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down Expand Up @@ -469,9 +470,10 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = (u8 *)(contents.data() + rel.r_offset);

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down
6 changes: 4 additions & 2 deletions elf/arch-i386.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -393,9 +393,10 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = base + rel.r_offset;

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down Expand Up @@ -476,9 +477,10 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = (u8 *)(contents.data() + rel.r_offset);

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down
6 changes: 4 additions & 2 deletions elf/arch-m68k.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -225,9 +225,10 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = base + rel.r_offset;

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down Expand Up @@ -266,8 +267,9 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down
6 changes: 4 additions & 2 deletions elf/arch-ppc32.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -297,9 +297,10 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = base + rel.r_offset;

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down Expand Up @@ -339,8 +340,9 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down
6 changes: 4 additions & 2 deletions elf/arch-ppc64v1.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -290,9 +290,10 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = base + rel.r_offset;

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down Expand Up @@ -348,8 +349,9 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down
6 changes: 4 additions & 2 deletions elf/arch-ppc64v2.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -284,9 +284,10 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = base + rel.r_offset;

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down Expand Up @@ -342,8 +343,9 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down
6 changes: 4 additions & 2 deletions elf/arch-riscv.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -548,9 +548,10 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = base + rel.r_offset;

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down Expand Up @@ -660,8 +661,9 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down
6 changes: 4 additions & 2 deletions elf/arch-s390x.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -339,9 +339,10 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = base + rel.r_offset;

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down Expand Up @@ -399,8 +400,9 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down
6 changes: 4 additions & 2 deletions elf/arch-sh4.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -275,9 +275,10 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = base + rel.r_offset;

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down Expand Up @@ -316,8 +317,9 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down
6 changes: 4 additions & 2 deletions elf/arch-sparc64.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -429,9 +429,10 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = base + rel.r_offset;

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down Expand Up @@ -491,8 +492,9 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down
6 changes: 4 additions & 2 deletions elf/arch-x86-64.cc
View file
Original file line number Diff line number Diff line change
Expand Up @@ -538,9 +538,10 @@ void InputSection<E>::apply_reloc_nonalloc(Context<E> &ctx, u8 *base) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = base + rel.r_offset;

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down Expand Up @@ -635,9 +636,10 @@ void InputSection<E>::scan_relocations(Context<E> &ctx) {
continue;

Symbol<E> &sym = *file.symbols[rel.r_sym];
const ElfSym<E> &esym = file.elf_syms[rel.r_sym];
u8 *loc = (u8 *)(contents.data() + rel.r_offset);

if (!sym.file) {
if (!is_resolved(sym, esym)) {
record_undef_error(ctx, rel);
continue;
}
Expand Down
35 changes: 5 additions & 30 deletions elf/input-files.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -1020,18 +1020,6 @@ void ObjectFile<E>::claim_unresolved_symbols(Context<E> &ctx) {
if (!this->is_alive)
return;

auto report_undef = [&](Symbol<E> &sym) {
std::stringstream ss;
if (std::string_view source = this->get_source_name(); !source.empty())
ss << ">>> referenced by " << source << "\n";
else
ss << ">>> referenced by " << *this << "\n";

typename decltype(ctx.undef_errors)::accessor acc;
ctx.undef_errors.insert(acc, {sym.name(), {}});
acc->second.push_back(ss.str());
};

for (i64 i = this->first_global; i < this->elf_syms.size(); i++) {
const ElfSym<E> &esym = this->elf_syms[i];
Symbol<E> &sym = *this->symbols[i];
Expand All @@ -1040,17 +1028,9 @@ void ObjectFile<E>::claim_unresolved_symbols(Context<E> &ctx) {

std::scoped_lock lock(sym.mu);

// If a protected/hidden undefined symbol is resolved to an
// imported symbol, it's handled as if no symbols were found.
if (sym.file && sym.file->is_dso &&
(sym.visibility == STV_PROTECTED || sym.visibility == STV_HIDDEN)) {
report_undef(sym);
continue;
}

if (sym.file &&
(!sym.esym().is_undef() || sym.file->priority <= this->priority))
continue;
if (sym.file)
if (!sym.esym().is_undef() || sym.file->priority <= this->priority)
continue;

// If a symbol name is in the form of "foo@version", search for
// symbol "foo" and check if the symbol has version "version".
Expand Down Expand Up @@ -1094,9 +1074,6 @@ void ObjectFile<E>::claim_unresolved_symbols(Context<E> &ctx) {
continue;
}

if (ctx.arg.unresolved_symbols == UNRESOLVED_WARN)
report_undef(sym);

// Traditionally, remaining undefined symbols cause a link failure
// only when we are creating an executable. Undefined symbols in
// shared objects are promoted to dynamic symbols, so that they'll
Expand All @@ -1107,15 +1084,13 @@ void ObjectFile<E>::claim_unresolved_symbols(Context<E> &ctx) {
// promoted to dynamic symbols for compatibility with other linkers.
// Some major programs, notably Firefox, depend on the behavior
// (they use this loophole to export symbols from libxul.so).
if (ctx.arg.shared && sym.visibility != STV_HIDDEN &&
(!ctx.arg.z_defs || ctx.arg.unresolved_symbols != UNRESOLVED_ERROR)) {
if (ctx.arg.shared && sym.visibility != STV_HIDDEN && !ctx.arg.z_defs) {
claim(true);
continue;
}

// Convert remaining undefined symbols to absolute symbols with value 0.
if (ctx.arg.unresolved_symbols != UNRESOLVED_ERROR || ctx.arg.noinhibit_exec)
claim(false);
claim(false);
}
}

Expand Down
24 changes: 24 additions & 0 deletions elf/mold.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -2830,4 +2830,28 @@ inline bool relax_tlsdesc(Context<E> &ctx, Symbol<E> &sym) {
return ctx.arg.relax && !ctx.arg.shared && !sym.is_imported;
}

// Returns true if esym has already been resolved.
template <typename E>
bool is_resolved(Symbol<E> &sym, const ElfSym<E> &esym) {
assert(sym.file);

// A non-weak undefined symbol must be promoted to an imported
// symbol or resolved to an defined symbol. Otherwise, it's an
// undefined symbol error.
//
// Every ELF file has an absolute local symbol as its first symbol.
// Referring to that symbol is always valid.
bool is_undef = esym.is_undef() && !esym.is_weak() && sym.sym_idx;
if (!sym.is_imported && is_undef && sym.esym().is_undef())
return false;

// If a protected/hidden undefined symbol is resolved to other .so,
// it's handled as if no symbols were found.
if (sym.file->is_dso &&
(sym.visibility == STV_PROTECTED || sym.visibility == STV_HIDDEN))
return false;

return true;
}

} // namespace mold::elf
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