Compact InputSectionData from 64 to 48 bytes

[ruiu]

ELF/InputSection.h

62–63

My preference is to use std::vector instead of char * and size.

[• rafael]

ELF/InputSection.h

62–63

std::vector is still 3 pointers.

What I want to do next is to always have a valid StringRef (or ArrayRef) with the data. Initially it points to the mmaped file. After decompression it points to UncompressedData and UncompressedDataSize can be removed.

[ruiu]

LGTM

[silvas]

ELF/InputSection.h

62

Orthogonal to Rui's concerns, this needs to be std::unique_ptr<char[]> for operator delete[] to be called. Otherwise, it will delete just a single char and corrupt the heap.

[Eugene.Zelenko]

Committed in r281084.

ELF/InputSection.h

public:
 
   // Used for garbage collection.
   unsigned Live : 1;
 
   unsigned Compressed : 1;
 
   uint32_t Alignment;
 
-  // If a section is compressed, this vector has uncompressed section data.
-  SmallVector<char, 0> Uncompressed;
+  // If a section is compressed, this has the uncompressed section data.
+  std::unique_ptr<char> UncompressedData;
+  size_t UncompressedDataSize = 0;
 
   std::vector<Relocation> Relocations;
 };
 
 // This corresponds to a section of an input file.
 template <class ELFT> class InputSectionBase : public InputSectionData {
 protected:
   typedef typename ELFT::Chdr Elf_Chdr;

ELF/InputSection.cpp

 
 template <class ELFT> StringRef InputSectionBase<ELFT>::getSectionName() const {
   return check(File->getObj().getSectionName(this->Header));
 }
 
 template <class ELFT>
 ArrayRef<uint8_t> InputSectionBase<ELFT>::getSectionData() const {
   if (Compressed)
-    return ArrayRef<uint8_t>((const uint8_t *)Uncompressed.data(),
-                             Uncompressed.size());
+    return ArrayRef<uint8_t>((const uint8_t *)UncompressedData.get(),
+                             UncompressedDataSize);
   return check(this->File->getObj().getSectionContents(this->Header));
 }
 
 // Returns a string for an error message.
 template <class SectionT> static std::string getName(SectionT *Sec) {
   return (Sec->getFile()->getName() + "(" + Sec->getSectionName() + ")").str();
 }
 
template <class ELFT> void InputSectionBase<ELFT>::uncompress() {
 
   auto *Hdr = reinterpret_cast<const Elf_Chdr *>(Data.data());
   Data = Data.slice(sizeof(Elf_Chdr));
 
   if (Hdr->ch_type != ELFCOMPRESS_ZLIB)
     fatal(getName(this) + ": unsupported compression type");
 
   StringRef Buf((const char *)Data.data(), Data.size());
-  if (zlib::uncompress(Buf, Uncompressed, Hdr->ch_size) != zlib::StatusOK)
+  UncompressedDataSize = Hdr->ch_size;
+  UncompressedData.reset(new char[UncompressedDataSize]);
+  if (zlib::uncompress(Buf, UncompressedData.get(), UncompressedDataSize) !=
+      zlib::StatusOK)
     fatal(getName(this) + ": error uncompressing section");
 }
 
 template <class ELFT>
 typename ELFT::uint
 InputSectionBase<ELFT>::getOffset(const DefinedRegular<ELFT> &Sym) const {
   return getOffset(Sym.Value);
 }