Hi Greg,
I tried using "_$" and "lldb$" as our private prefix, both of these solves the
issue and works fine for MIPS.
-Regards,
Bhushan
-Original Message-
From: Greg Clayton [mailto:gclay...@apple.com]
Sent: 23 October 2015 22:29
To: Bhushan Attarde
Cc: lldb-dev@lists.llvm.org
Subject: Re: [lldb-dev] llvm assertion while evaluating expressions for MIPS on
Linux
What happens if we go with "_$" as our private prefix? Or maybe "lldb$"? Would
this avoid the issue and fix things for MIPS? I would rather us have a
consistent private naming scheme across all architectures. Let me know if you
can try that out and let us know if this works.
Greg
> On Oct 23, 2015, at 5:03 AM, Bhushan Attarde
> wrote:
>
> Hi Greg,
>
> Thanks for your reply.
>
> There are different temporary symbols for different architectures and file
> formats.
> As far as I could see, llvm::MCAsmInfo class has a member
> "PrivateGlobalPrefix" which specifies this temporary symbol.
> The default value for PrivateGlobalPrefix is 'L' (for ELF it is ".L").
> The subclasses of llvm::MCAsmInfo sets PrivateGlobalPrefix to whatever value
> they want to use for temporary symbol.
> MIPS sets this to "$". (and X86/ARM uses ".L")
>
> Since the function name "$__lldb_valid_pointer_check" starts with "$" it
> matches with PrivateGlobalPrefix for MIPS and hence it is marked as temporary.
> Its fine for all x86/x86_64/arm and arm64 variants because they all use
> symbol other than "$" (i.e ".L") as their PrivateGlobalPrefix.
>
> As you mentioned we cannot remove "$" from function name because it
> may conflict with symbols from system libraries or user binaries, so do you
> think removing C Language linkage from function "$__lldb_valid_pointer_check"
> can be a solution? or do you have a better solution to this issue?
>
> Regards,
> Bhushan
>
>
> -Original Message-
> From: Greg Clayton [mailto:gclay...@apple.com]
> Sent: 20 October 2015 23:56
> To: Greg Clayton
> Cc: Bhushan Attarde; lldb-dev@lists.llvm.org
> Subject: Re: [lldb-dev] llvm assertion while evaluating expressions
> for MIPS on Linux
>
> My guess is that there is a different temporary symbol for differing
> architectures and possibly depending on which file format (mach-o or ELF) you
> are targeting. MIPS probably happens to use '$'. I know mach-o files use "L"
> as the temporary symbol prefix, ELF tends to use '.'. Not sure where this
> would be abstracted in LLVM or if it is just built into the assemblers
> directly for each arch... If you can find out where this can be detected
> within LLVM, we can make sure we don't use any temporary prefixes in symbol
> names and work around this issue. We need to make sure that any functions we
> generate and JIT up and insert into the program do not conflict with _any_
> symbol that could be in any system libraries or user binaries. This is why we
> used '$' in the first place.
>
> Greg
>
>> On Oct 20, 2015, at 11:11 AM, Greg Clayton via lldb-dev
>> wrote:
>>
>> What is this not happening on any other architecture? Is the "$" special for
>> MIPS and not for other architectures? We really don't want to remove the '$'
>> as we want the symbol to be unique. The '$' symbol is fine for all
>> x86/x86_64/arm and arm64 variants...
>>
>> Greg
>>
>>
>>> On Oct 19, 2015, at 11:30 PM, Bhushan Attarde via lldb-dev
>>> wrote:
>>>
>>> Hi,
>>>
>>> I am facing issue (llvm assertion) in evaluating expressions for MIPS on
>>> Linux.
>>>
>>> (lldb) p fooptr(a,b)
>>> lldb: /home/battarde/git/llvm/lib/MC/ELFObjectWriter.cpp:791: void
>>> {anonymous}::ELFObjectWriter::computeSymbolTable(llvm::MCAssembler&, const
>>> llvm::MCAsmLayout&, const SectionIndexMapTy&, const RevGroupMapTy&,
>>> {anonymous}::ELFObjectWriter::SectionOffsetsTy&): Assertion `Local ||
>>> !Symbol.isTemporary()' failed.
>>>
>>> I debugged it and found that, LLDB inserts calls to dynamic checker
>>> function for pointer validation at appropriate locations in expression’s IR.
>>>
>>> The issue is that this checker function’s name (hard-coded in LLDB in
>>> lldb\source\Expression\IRDynamicChecks.cpp) starts with “$” i.e
>>> “$__lldb_valid_pointer_check”.
>>> While creating a MCSymbol (MCContext::createSymbol() in
>>> llvm/lib/MC/MCContext.cpp) for this function llvm detects the name starts
>>> with “$” and marks that symbol as ‘temporary’ symbol (PrivateGlobalPrefix
>>> is '$' for MIPS) Further while computing a symbol table in
>>> ELFObjectWriter::computeSymbolTable() the assertion triggers because this
>>> symbol is 'temporary'.
>>>
>>> I tried couple of things that solves this issue for MIPS.
>>>
>>> 1. Remove '$' from the function name.
>>> 2. Remove "C Language linkage" from the dynamic pointer validation
>>> function i.e the below piece of code in
>>> lldb\source\Expression\IRDynamicChecks.cpp
>>>
>>> - static const char g_valid_pointer_check_text[]
