Vscode-cpptools: Macro expansion fails to fully work with clang/gcc

[sean-mcmanus]

Does this only expand one level of macros?

That is, if I have two macros like

#define BAR(l,r) (l + r)
#define FOO(x) BAR(x,2)

and I write FOO(1) I would want this to say "Expands to (1 + 2)" since that is the final fully expanded form. Instead, it seems to say "Expands to BAR(1,2)" which is much less useful.

Or if showing the final form immediately isn't desirable maybe an way to trigger further expansion. Many macros are multiple levels in practice and the first expansion only doens't show much.

_Originally posted by @travisdowns in https://github.com/Microsoft/vscode-cpptools/issues/1734#issuecomment-488921102_

[sean-mcmanus]

@travisdowns I'm not able to repro the issue. It fully expands for me. Can you give more repro details, such as your extension version, OS, compilerPath/intelliSenseMode, etc.?

[travisdowns]

C/C++ extension v0.22.1
vscode 1.33.1
Ubuntu 16.04

here's my c_cpp json:

{
    "configurations": [
        {
            "name": "Linux",
            "includePath": [
                "${workspaceFolder}/**"
            ],
            "defines": ["STRIDE=64", "_GNU_SOURCE"],
            "compilerPath": "/usr/bin/gcc -march=haswell",
            "cStandard": "c11",
            "cppStandard": "c++11",
            "intelliSenseMode": "${default}",
            "browse": {
                "limitSymbolsToIncludedHeaders": true
            }
        }
    ],
    "version": 4
}

[sean-mcmanus]

Okay, thanks for reporting this -- I repro it with WSL/gcc mode. Looks like there is an unexpected behavior difference in that case (seems like a bug).

[sean-mcmanus]

The bug repros with VS 2019 -- I've reported the bug there: https://developercommunity.visualstudio.com/content/problem/556656/c-intellisense-macro-expansion-fails-to-fully-work.html . If you have a "Microsoft account" you could upvote that.

[eruanno123]

Hi, I work with WSL2/gcc and noticed that macros are not expanded recursively. Then I found this issue open since May 2019.
Any chance to solve this issue in the nearest future?

[sean-mcmanus]

The issue needs more upvotes on the developer community site.

[lucaszanella]

Still suffering from this. Very hard to read source codes, specially linux kernel which relies on lots of nested macros :(

[sean-mcmanus]

@lucaszanella I mentioned at https://developercommunity.visualstudio.com/content/problem/556656/c-intellisense-macro-expansion-fails-to-fully-work.html that the VS Code issue has more upvotes (versus the 2 on their page).