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e6f558ca83
of casting the integer '4' to such a pointer. There is no reason to expect '4' to be a portable or reliable pointer of this form. The only reason this ever worked is because the PointerIntPair that this actually gets used with has an artificially *low* presumed alignment that allowed it to work. When the alignment of PointerIntPair is derived from the actual type's alignment, the asserts start firing on this pointer. I'm amazed we never managed to do anything that triggered the alignment sanitizer with it, as this is just flat out UB. If folks dislike this approach to providing a sentinel fragment address, there are a myriad of other alternatives, suggestions welcome. But this one has the distinct advantage of not requiring the friend dance of ilist's sentinel (which I'll point out is *also* in play for MCFragment!) and seems to be using a nicely provided facility in MCFragment to establish just such dummy nodes. This is part of a series of patches to allow LLVM to check for complete pointee types when computing its pointer traits. This is absolutely necessary to get correct (or reproducible) results for things like how many low bits are guaranteed to be zero. llvm-svn: 256552
82 lines
2.8 KiB
C++
82 lines
2.8 KiB
C++
//===- lib/MC/MCSymbol.cpp - MCSymbol implementation ----------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/MC/MCAsmInfo.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/ErrorHandling.h"
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#include "llvm/Support/raw_ostream.h"
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using namespace llvm;
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// Only the address of this fragment is ever actually used.
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static MCDummyFragment SentinelFragment(nullptr);
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// Sentinel value for the absolute pseudo fragment.
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MCFragment *MCSymbol::AbsolutePseudoFragment = &SentinelFragment;
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void *MCSymbol::operator new(size_t s, const StringMapEntry<bool> *Name,
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MCContext &Ctx) {
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// We may need more space for a Name to account for alignment. So allocate
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// space for the storage type and not the name pointer.
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size_t Size = s + (Name ? sizeof(NameEntryStorageTy) : 0);
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// For safety, ensure that the alignment of a pointer is enough for an
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// MCSymbol. This also ensures we don't need padding between the name and
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// symbol.
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static_assert((unsigned)AlignOf<MCSymbol>::Alignment <=
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AlignOf<NameEntryStorageTy>::Alignment,
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"Bad alignment of MCSymbol");
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void *Storage = Ctx.allocate(Size, alignOf<NameEntryStorageTy>());
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NameEntryStorageTy *Start = static_cast<NameEntryStorageTy*>(Storage);
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NameEntryStorageTy *End = Start + (Name ? 1 : 0);
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return End;
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}
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void MCSymbol::setVariableValue(const MCExpr *Value) {
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assert(!IsUsed && "Cannot set a variable that has already been used.");
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assert(Value && "Invalid variable value!");
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assert((SymbolContents == SymContentsUnset ||
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SymbolContents == SymContentsVariable) &&
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"Cannot give common/offset symbol a variable value");
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this->Value = Value;
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SymbolContents = SymContentsVariable;
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setUndefined();
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}
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void MCSymbol::print(raw_ostream &OS, const MCAsmInfo *MAI) const {
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// The name for this MCSymbol is required to be a valid target name. However,
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// some targets support quoting names with funny characters. If the name
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// contains a funny character, then print it quoted.
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StringRef Name = getName();
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if (!MAI || MAI->isValidUnquotedName(Name)) {
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OS << Name;
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return;
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}
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if (MAI && !MAI->supportsNameQuoting())
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report_fatal_error("Symbol name with unsupported characters");
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OS << '"';
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for (char C : Name) {
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if (C == '\n')
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OS << "\\n";
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else if (C == '"')
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OS << "\\\"";
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else
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OS << C;
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}
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OS << '"';
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}
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#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
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void MCSymbol::dump() const { dbgs() << *this; }
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#endif
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