Thank you for explanations! I'll create the converter to DWARF expressions.
Regards, Aleksandr On Wed, Jun 27, 2018 at 5:38 PM Greg Clayton <clayb...@gmail.com> wrote: > > > On Jun 27, 2018, at 5:25 AM, Aleksandr Urakov via lldb-dev < > lldb-dev@lists.llvm.org> wrote: > > Hello! > > We want to add to LLDB a support of a lookup of variables values with PDB. > > Now SymbolFilePDB::ParseVariableForPDBData function uses an empty location > for variables, so e.g. `fr v` prints values as '<empty constant data>'. Symbol > location information is available in a PDB (through > PDBSymbolData::getLocationType and so on), but not in the format of DWARF > expression. Do I understand correctly, that it is necessary to write some > converter of a PDB symbol location to a DWARF expression bytecode? Is this > the preferable way of solving the issue? What are pitfalls there? Please, > share your thoughts on this. > > > DWARF expressions are pretty powerful and provide all the opcode need to > describe variable locations. You will need to covert the PDB location to > the DWARF expression opcodes. > > Some examples: > variable is at SP + 4 = DW_OP_bregXXX(4) > > DW_OP_bregXXX where XXX is the register number for your stack pointer. > This opcode takes a single operand that is the offset from the register in > question. The variable value is expected to be at the load address in > memory. > > variable is in register 12 = DW_OP_reg12 > > There are 32 DW_OP_regXXX opcodes DW_OP_reg0 - DW_OP_reg31. If your > register value is higher than 32, then use DW_OP_regx which takes a ULEB128 > parameter which is the register number: > > variable is in register 46 = DW_OP_regx(46) > > Global variables: > > variable is at file address 0x12340000 = DW_OP_addr(0x12340000) > > The address here is a file address, or the file VM address of the global > as it is known in the object file. This address will be slid and covered to > a load address if needed at runtime. > > IF you have any other questions on converting your locations, let me know. > But the above examples should give you a good start. > > Greg > > > Regards, > Aleksandr > > -- > Aleksandr Urakov > Software Developer > JetBrains > http://www.jetbrains.com > The Drive to Develop > _______________________________________________ > lldb-dev mailing list > lldb-dev@lists.llvm.org > http://lists.llvm.org/cgi-bin/mailman/listinfo/lldb-dev > > > -- Aleksandr Urakov Software Developer JetBrains http://www.jetbrains.com The Drive to Develop
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