[llvm] r221444 - Object, COFF: Infer symbol sizes from adjacent symbols

[Rafael Espíndola]

thanks!

On 6 November 2014 03:10, David Majnemer <david.majnemer at gmail.com> wrote:
> Author: majnemer
> Date: Thu Nov  6 02:10:41 2014
> New Revision: 221444
>
> URL: http://llvm.org/viewvc/llvm-project?rev=221444&view=rev
> Log:
> Object, COFF: Infer symbol sizes from adjacent symbols
>
> Use the position of the subsequent symbol in the object file to infer
> the size of it's predecessor.  I hope to eventually remove whatever COFF
> specific details from this little algorithm so that we can unify this
> logic with what Mach-O does.
>
> Modified:
>     llvm/trunk/lib/Object/COFFObjectFile.cpp
>     llvm/trunk/test/Object/nm-trivial-object.test
>
> Modified: llvm/trunk/lib/Object/COFFObjectFile.cpp
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/Object/COFFObjectFile.cpp?rev=221444&r1=221443&r2=221444&view=diff
> ==============================================================================
> --- llvm/trunk/lib/Object/COFFObjectFile.cpp (original)
> +++ llvm/trunk/lib/Object/COFFObjectFile.cpp Thu Nov  6 02:10:41 2014
> @@ -250,20 +250,52 @@ std::error_code COFFObjectFile::getSymbo
>        return object_error::success;
>      }
>    }
> -  // FIXME: Return the correct size. This requires looking at all the symbols
> -  //        in the same section as this symbol, and looking for either the next
> -  //        symbol, or the end of the section.
> +
> +  // Let's attempt to get the size of the symbol by looking at the address of
> +  // the symbol after the symbol in question.
> +  uint64_t SymbAddr;
> +  if (std::error_code EC = getSymbolAddress(Ref, SymbAddr))
> +    return EC;
>    int32_t SectionNumber = Symb.getSectionNumber();
> -  if (!COFF::isReservedSectionNumber(SectionNumber)) {
> +  if (COFF::isReservedSectionNumber(SectionNumber)) {
> +    // Absolute and debug symbols aren't sorted in any interesting way.
> +    Result = 0;
> +    return object_error::success;
> +  }
> +  const section_iterator SecEnd = section_end();
> +  uint64_t AfterAddr = UnknownAddressOrSize;
> +  for (const symbol_iterator &SymbI : symbols()) {
> +    section_iterator SecI = SecEnd;
> +    if (std::error_code EC = SymbI->getSection(SecI))
> +      return EC;
> +    // Check the symbol's section, skip it if it's in the wrong section.
> +    // First, make sure it is in any section.
> +    if (SecI == SecEnd)
> +      continue;
> +    // Second, make sure it is in the same section as the symbol in question.
> +    if (!sectionContainsSymbol(SecI->getRawDataRefImpl(), Ref))
> +      continue;
> +    uint64_t Addr;
> +    if (std::error_code EC = SymbI->getAddress(Addr))
> +      return EC;
> +    // We want to compare our symbol in question with the closest possible
> +    // symbol that comes after.
> +    if (AfterAddr > Addr && Addr > SymbAddr)
> +      AfterAddr = Addr;
> +  }
> +  if (AfterAddr == UnknownAddressOrSize) {
> +    // No symbol comes after this one, assume that everything after our symbol
> +    // is part of it.
>      const coff_section *Section = nullptr;
>      if (std::error_code EC = getSection(SectionNumber, Section))
>        return EC;
> -
>      Result = Section->SizeOfRawData - Symb.getValue();
> -    return object_error::success;
> +  } else {
> +    // Take the difference between our symbol and the symbol that comes after
> +    // our symbol.
> +    Result = AfterAddr - SymbAddr;
>    }
>
> -  Result = 0;
>    return object_error::success;
>  }
>
>
> Modified: llvm/trunk/test/Object/nm-trivial-object.test
> URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/Object/nm-trivial-object.test?rev=221444&r1=221443&r2=221444&view=diff
> ==============================================================================
> --- llvm/trunk/test/Object/nm-trivial-object.test (original)
> +++ llvm/trunk/test/Object/nm-trivial-object.test Thu Nov  6 02:10:41 2014
> @@ -1,6 +1,6 @@
> -RUN: yaml2obj %p/Inputs/COFF/i386.yaml | llvm-nm -a - \
> +RUN: yaml2obj %p/Inputs/COFF/i386.yaml | llvm-nm -a -S - \
>  RUN:         | FileCheck %s -check-prefix COFF
> -RUN: yaml2obj %p/Inputs/COFF/x86-64.yaml | llvm-nm -a - \
> +RUN: yaml2obj %p/Inputs/COFF/x86-64.yaml | llvm-nm -a -S - \
>  RUN:         | FileCheck %s -check-prefix COFF
>  RUN: llvm-nm %p/Inputs/trivial-object-test.elf-i386 \
>  RUN:         | FileCheck %s -check-prefix ELF
> @@ -49,11 +49,11 @@ RUN: llvm-nm | FileCheck %s -check-prefi
>  REQUIRES: shell
>
>
> -COFF: 00000000 d .data
> -COFF: 00000000 t .text
> -COFF: 00000000 d L{{_?}}.str
> +COFF: 00000000 {{.*}} d .data
> +COFF: 00000000 {{.*}} t .text
> +COFF: 00000000 0000000d d L{{_?}}.str
>  COFF:          U {{_?}}SomeOtherFunction
> -COFF: 00000000 T {{_?}}main
> +COFF: 00000000 {{.*}} T {{_?}}main
>  COFF:          U {{_?}}puts
>
>  COFF-COMMON: 00000000 00000000 b .bss
>
>
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