Definitions passed via compile_commands.json (using CMake), gets parsed wrong.

[omicronns]

Type: LanguageService

Definitions from compile_commands.json gets parsed wrong. If I want to pass definition via CMake I add following statement in CMakeLists.txt:

add_definitions("-D__weak=__attribute__((weak))" -DABC=\"asd\")

Now __weak should be replaced with __attribute__((weak)) in code, and ABC should be replaced with "asd" string literal. At least that how compiler behaves. Instead if I hover over __weak i get #define __weak "__attribute__((weak))" which is incorrect. Also if i hover over ABC i get proper information #define ABC "asd". This happens only when definition contains one or more characters that have to be escaped, so if I set __weak definition to __attribute__ it gets passed correctly. It happens because without need to escape characters, part after = in definition does not get wrapped in " by CMake. So instead -D__weak="__attribute__((weak))" on command line appears -D__weak=__attribute__.
This also causes problem to be reported (but it is due to invalid __weak value):

{
	"resource": "vscode-intelisense/lib.cxx",
	"owner": "_generated_diagnostic_collection_name_#0",
	"code": "undefined",
	"severity": 8,
	"message": "expected a declaration",
	"startLineNumber": 1,
	"startColumn": 1,
	"endLineNumber": 1,
	"endColumn": 2
}

• OS and Version: Linux 4.17.6-1-ARCH
• VS Code Version: 1.25.1
• C/C++ Extension Version: 0.17.7
• Clang Version: 6.0.1

To Reproduce

Example:
c_cpp_properties.json

{
    "configurations": [
        {
            "name": "Linux",
            "includePath": [
                "${workspaceFolder}/**"
            ],
            "defines": [],
            "compilerPath": "/usr/bin/clang",
            "cStandard": "c11",
            "cppStandard": "c++17",
            "intelliSenseMode": "clang-x64",
            "compileCommands": "${workspaceFolder}/build/compile_commands.json"
        }
    ],
    "version": 4
}

lib.cxx

__weak void foo() {ABC;}

CMakeLists.txt

cmake_minimum_required(VERSION 3.0 FATAL_ERROR)

project(vscode-intelisense)

set(CMAKE_EXPORT_COMPILE_COMMANDS "1")

set(CMAKE_CXX_STANDARD 17)

add_library(${PROJECT_NAME} STATIC lib.cxx)
add_definitions("-D__weak=__attribute__((weak))" -DABC=\"asd\")

Steps to reproduce the behavior:

1. Recreate file structure:

vscode-intelisense
  |
  |-lib.cxx
  |-CMakeLists.txt
  .vscode
    |-c_cpp_properties.json

2. Build with rm -rf build && cmake . -Bbuild && VERBOSE=1 cmake --build build inside vscode-intelisense folder.
3. Open vscode-intelisense directory in vscode.
4. Hover over __weak and ABC in lib.cxx.

Expected behavior

__weak definition to be recognized correctly as __attribute__((weak)) instead "__attribute__((weak))".
No problems reported.

[bobbrow]

If you could share the compile commands entry that uses this define, that would be the fastest way for us to diagnose the problem. Otherwise, we'll take a look at generating one next week when we get back in the office.

[omicronns]

Sure.
compile_commands.json

[
{
  "directory": "vscode-intelisense/build",
  "command": "/usr/bin/c++  -DABC=\\\"asd\\\" -D__weak=\"__attribute__((weak))\"    -std=gnu++1z -o CMakeFiles/vscode.dir/lib.cxx.o -c vscode-intelisense/lib.cxx",
  "file": "vscode-intelisense/lib.cxx"
}
]

[sean-mcmanus]

You're telling the compiler to define __weak to be "__attribute__((weak))", i.e. a value assignable to a std::string. Can you use add_definitions(-D__weak=__attribute__((weak))) instead? That works for me.

[omicronns]

This add_definitions(-D__weak=__attribute__((weak)) -DABC=\"asd\") gives me a compile error.

/bin/sh: -c: line 0: syntax error near unexpected token `('
/bin/sh: -c: line 0: `/usr/bin/c++  -D__weak=__attribute__  ( ( weak ) ) -std=gnu++1z -o CMakeFiles/vscode-intelisense.dir/lib.cxx.o -c /home/kad/Projects/test/lib.cxx'

Escaping parentheses add_definitions(-D__weak=__attribute__\(\(weak\)\) -DABC=\"asd\") gives me same behaviour as in original issue.

Also I think parenthesising whole "-D..." expression is not the same as parenthesising -D...="...".

[bobbrow]

@sean-mcmanus, this looks like it could be a bug. Note that -DABC is using \\\" to inject a double quote into the value. I'll take a look.

[omicronns]

I noticed earlier, that on windows i got different compile_commands.json. When i run cmake on windows at least with mingw generator, it gets generated like -D__weak=__attribute__((weak)) without any escaped quotes like \".

[bobbrow]

I just looked at the tests and we don't have any for this case. That's probably why we missed it.

[sean-mcmanus]

The parsing issues with compile_commands.json definitions should be fixed with 0.19.0 -- I think part of the fix made it into 0.18.0, but there were additional fixes afterwards.