[lld] r281989 - Don't produce an error for undefined entry symbol.

[Rafael Espíndola via llvm-commits]

Yes, a warning is a good idea. I will add one.

Cheers,
Rafael


On 20 September 2016 at 13:34, Rui Ueyama <ruiu at google.com> wrote:
> This is interesting. I was thinking that in that case linkers should report
> an error, but GNU linkers actually report just a warning. Maybe we should
> report a warning, too.
>
> On Tue, Sep 20, 2016 at 10:14 AM, Rafael Espindola via llvm-commits
> <llvm-commits at lists.llvm.org> wrote:
>>
>> Author: rafael
>> Date: Tue Sep 20 12:14:16 2016
>> New Revision: 281989
>>
>> URL: http://llvm.org/viewvc/llvm-project?rev=281989&view=rev
>> Log:
>> Don't produce an error for undefined entry symbol.
>>
>> This is particularly important when the symbol comes from a linker
>> script. It is common to use the same linker script for shared
>> libraries and executables. Without this we would always fail to link
>> shared libraries with -z,defs and a linker script with an ENTRY
>> directive.
>>
>> Modified:
>>     lld/trunk/ELF/Driver.cpp
>>     lld/trunk/test/ELF/linkerscript/linkerscript.s
>>
>> Modified: lld/trunk/ELF/Driver.cpp
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/ELF/Driver.cpp?rev=281989&r1=281988&r2=281989&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/ELF/Driver.cpp (original)
>> +++ lld/trunk/ELF/Driver.cpp Tue Sep 20 12:14:16 2016
>> @@ -667,16 +667,15 @@ template <class ELFT> void LinkerDriver:
>>    // Note that AMDGPU binaries have no entries.
>>    if (!Config->Entry.empty()) {
>>      // It is either "-e <addr>" or "-e <symbol>".
>> -    if (Config->Entry.getAsInteger(0, Config->EntryAddr))
>> -      Config->EntrySym = Symtab.addUndefined(Config->Entry);
>> +    Config->Entry.getAsInteger(0, Config->EntryAddr);
>>    } else if (!Config->Shared && !Config->Relocatable &&
>>               Config->EMachine != EM_AMDGPU) {
>>      // -e was not specified. Use the default start symbol name
>>      // if it is resolvable.
>>      Config->Entry = (Config->EMachine == EM_MIPS) ? "__start" : "_start";
>> -    if (Symtab.find(Config->Entry))
>> -      Config->EntrySym = Symtab.addUndefined(Config->Entry);
>>    }
>> +  if (Symtab.find(Config->Entry))
>> +    Config->EntrySym = Symtab.addUndefined(Config->Entry);
>>
>>    if (HasError)
>>      return; // There were duplicate symbols or incompatible files
>>
>> Modified: lld/trunk/test/ELF/linkerscript/linkerscript.s
>> URL:
>> http://llvm.org/viewvc/llvm-project/lld/trunk/test/ELF/linkerscript/linkerscript.s?rev=281989&r1=281988&r2=281989&view=diff
>>
>> ==============================================================================
>> --- lld/trunk/test/ELF/linkerscript/linkerscript.s (original)
>> +++ lld/trunk/test/ELF/linkerscript/linkerscript.s Tue Sep 20 12:14:16
>> 2016
>> @@ -60,11 +60,10 @@
>>  # RUN: ld.lld -o %t2 %t.script %t
>>  # RUN: llvm-readobj %t2 > /dev/null
>>
>> +# The entry symbol should not cause an undefined error.
>>  # RUN: echo "ENTRY(_wrong_label)" > %t.script
>> -# RUN: not ld.lld -o %t2 %t.script %t > %t.log 2>&1
>> -# RUN: FileCheck -check-prefix=ERR-ENTRY %s < %t.log
>> -
>> -# ERR-ENTRY: undefined symbol: _wrong_label
>> +# RUN: ld.lld -o %t2 %t.script %t
>> +# RUN: ld.lld --entry=abc -o %t2 %t
>>
>>  # -e has precedence over linker script's ENTRY.
>>  # RUN: echo "ENTRY(_label)" > %t.script
>>
>>
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>
>