The spec does say they occur in the same order, which strongly implies that there is a DW_TAG_call_site_parameter for each actual parameter. Although, now that I say that, I have a memory of some discussion where a parameter entry might be omitted entirely. I don’t remember the details, but Jakub probably does. The spec does not clearly say that parameter entries can be omitted, though. --paulr
From: Sergey <spevne...@gmail.com> Sent: Friday, June 14, 2024 1:12 PM To: dwarf-discuss@lists.dwarfstd.org; Robinson, Paul <paul.robin...@sony.com> Subject: RE: [Dwarf-discuss] Request for clarification of handling stack-passed parameters In that case I shall create appropriate issues for the mentioned compilers in order to discuss the matter with them. I think I have found another issue with clang. In some cases it does not generate middle parameters: namely, it skipped the 2nd one yet included the 3rd one. It believe it does not match the standard (p91 line 6-7): "Call site parameter entries occur in the same order as the corresponding parameters in the source.", does it? On Jun 14, 2024, 15:11 +0300, Robinson, Paul <paul.robin...@sony.com<mailto:paul.robin...@sony.com>>, wrote: I believe this is an issue with the implementations, although it is a bit odd that both gcc and clang behave the same way. There should be a DW_TAG_call_site_parameter for each parameter. DW_AT_location should describe the stack slot where the parameter is passed. It should not be a problem for the compiler to do that, the location description would be evaluated in the context of the caller. --paulr From: Dwarf-discuss <dwarf-discuss-bounces+paul.robinson=sony....@lists.dwarfstd.org<mailto:dwarf-discuss-bounces+paul.robinson=sony....@lists.dwarfstd.org>> On Behalf Of Sergey via Dwarf-discuss Sent: Wednesday, June 12, 2024 9:57 AM To: dwarf-discuss@lists.dwarfstd.org<mailto:dwarf-discuss@lists.dwarfstd.org> Subject: [Dwarf-discuss] Request for clarification of handling stack-passed parameters # Request for clarification of handling stack-passed parameters ## Background I came across this while parsing parameters of a variadic function in C. Formal parameters are not sufficient for my case, since all the variadic arguments are described with a single `DW_TAG_unspecified_parameters`, whereas reading `DW_TAG_call_site_parameter` allows to get their locations and values. ## Overview When generating a DWARF5 of a C function with **more than 6** parameters, the generated `DW_TAG_call_site` contains only **first 6** `DW_TAG_call_site_parameter`s (function's `DW_TAG_formal_parameter`s contain all of them). Something I have noticed is that the parameters, which do not get `DW_TAG_call_site_parameter` generated, are all **passed through stack**(whereas first 6 through registers), as evident by function's `DW_TAG_formal_parameter`'s `DW_AT_location` containing `DW_OP_fbreg`. ## Request for clarification It happens both with gcc and clang, however I was unable to find any information in the standard regarding generation of only registed-passed parameters. I request clarification on whether it is an issue with implementations, or is there something in the standard which justifies the described behaviour.
-- Dwarf-discuss mailing list Dwarf-discuss@lists.dwarfstd.org https://lists.dwarfstd.org/mailman/listinfo/dwarf-discuss
