Build: /Qspectre- is MSVC-only and breaks every Release target under clang-cl

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Since Oct 23, 2026.

  • #386 by @ahmedgamalalzatary — open

Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
88/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
cmake, cpp
Domain
build-system, tooling

Research direction

Start in ps2xRuntime/cmake/ReleaseMode.cmake at EnableFastReleaseMode() (around line 22), where /Qspectre- is added under if(MSVC). Guard that one flag so it is omitted when CMAKE_CXX_COMPILER_ID matches Clang (clang-cl). Confirm Release builds of the listed targets succeed with clang-cl; /GL can stay as a warning-only unused argument.

Written by the indexing model from the issue text.

Description

What happens

EnableFastReleaseMode() (ps2xRuntime/cmake/ReleaseMode.cmake:22) adds 12 optimisation flags under an if(MSVC) guard. CMake sets MSVC to 1 for any MSVC-like command-line frontend, clang-cl included. Eleven of those flags are fine under clang-cl; the twelfth, /Qspectre-, is cl.exe-only. clang-cl does not recognise it, treats it as an input file name, and fails:

clang-cl: error: no such file or directory: '/Qspectre-'; did you mean '/Qspectre'?

Every target that calls EnableFastReleaseMode therefore fails to compile in Release under clang-cl -- ps2_recomp_lib, ps2_recomp, ps2_analyzer_lib, ps2_analyzer, ps2_runtime, ps2EntryRunner, plus the ps2xStudio and ps2xTest targets. The whole project is blocked.

It is invisible under cl.exe, and it only hits the Windows + clang-cl combination -- the one worth recommending, since it builds our 2752-file runner in about 60 seconds.

Measured, flag by flag

Each of the 12 flags passed individually to clang-cl /c on a neutral translation unit:

/O2 /Ob2 /Oi /Gy /Gw /GF /Zc:inline /fp:fast /arch:AVX2 /GS-    ok
/GL          ok, but "warning: argument unused during compilation: '/GL'"
/Qspectre-   REJECTED

At link time /LTCG /OPT:REF /OPT:ICF all work: the binary is produced and runs. So the problem is confined to this one compile flag.

Suggested fix

Keep the flag for a real cl.exe, drop it for clang-cl:

if(MSVC)
    set(_ps2x_cl_only_flags /Qspectre-)
    if(CMAKE_CXX_COMPILER_ID MATCHES "Clang")
        set(_ps2x_cl_only_flags "")
    endif()

    target_compile_options(${TargetName} PRIVATE
        $<$<CONFIG:Release>:
            ... the other 11 flags, unchanged ...
            /GS-
            ${_ps2x_cl_only_flags}
        >
    )

CMAKE_CXX_COMPILER_ID is Clang for clang-cl and MSVC for cl.exe, so the test separates exactly the two cases. With that change: 243 targets built, 0 errors.

Note that /GL is accepted but ignored at compile time under clang-cl (it warns). Not an error, but dead weight in that configuration.

Found while statically recompiling Ridge Racer V (NTSC-U, SLUS_200.02) with PS2Recomp.
Tested on commit 75d729ce; main was c5a9d02 at the time of writing, one README-only commit ahead.
Host: Windows 11 x64, clang-cl 22.1.3 + Ninja, MSVC toolset 14.51.36231, Windows SDK 10.0.26100.0, CMake 4.2.3.
None of these are specific to this game.

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