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Commits on Sep 12, 2026

  1. State that [[msvc::forceinline]] behaves similarly to __forceinline b… 

    …ut preserves the symbol in the TU

The documentation treated [[msvc::forceinline]] as a synonym of __forceinline, but
they don't have the same exact behavior. In a empirical test, a Link Time Optimization
enabled build of a static library had a method marked as __forceinline elided
from the final objects, causing a linking error when trying to consume the
static library from a non-LTO enabled exe or shared library. The method definition
is *not* present/visible in the header. Instead, [[msvc::forceinline]] was able to
both intra-optimize the static library and create a symbol for the annotated function,
allowing link from a consumer which has not visibility of the definition.

For more context, the behavior of [[msvc::forceinline]] aligns with the behavior
of the gcc specific always_inline[1] attribute, and clang also observes
the same behavior.

Below the results of a probe using VS 2026 and VS 2022.
-----------------------------------------------
== toolchains ==
-- 18 (18.10.12201.205): Visual Studio 18 2026
   C:\Program Files\Microsoft Visual Studio\18\Community
-- 2022 (17.14.37531.7): Visual Studio 17 2022
   C:\Program Files\Microsoft Visual Studio\2022\Community
-- cmake: cmake version 4.3.2

== results ==

VS      Annotation               LTO    Library    Exe               Shlib             Symbols     Note
----    ---------------------    ---    -------    --------------    --------------    --------    ----
18      none                     OFF    OK         LINK-OK RUN-OK    LINK-OK RUN-OK    present
18      none                     ON     OK         LINK-OK RUN-OK    LINK-OK RUN-OK    n/a (IL)
18      __forceinline            OFF    OK         LINK-FAIL         LINK-FAIL         absent
18      __forceinline            ON     OK         LINK-FAIL         LINK-FAIL         n/a (IL)
18      [[msvc::forceinline]]    OFF    OK         LINK-OK RUN-OK    LINK-OK RUN-OK    present
18      [[msvc::forceinline]]    ON     OK         LINK-OK RUN-OK    LINK-OK RUN-OK    n/a (IL)
2022    none                     OFF    OK         LINK-OK RUN-OK    LINK-OK RUN-OK    present
2022    none                     ON     OK         LINK-OK RUN-OK    LINK-OK RUN-OK    n/a (IL)
2022    __forceinline            OFF    OK         LINK-FAIL         LINK-FAIL         absent
2022    __forceinline            ON     OK         LINK-FAIL         LINK-FAIL         n/a (IL)
2022    [[msvc::forceinline]]    OFF    OK         LINK-OK RUN-OK    LINK-OK RUN-OK    present
2022    [[msvc::forceinline]]    ON     OK         LINK-OK RUN-OK    LINK-OK RUN-OK    n/a (IL)

== verdict ==
18 lto=OFF: PARITY, [[msvc::forceinline]] keeps the symbol where __forceinline drops it
18 lto=ON: PARITY, [[msvc::forceinline]] keeps the symbol where __forceinline drops it
2022 lto=OFF: PARITY, [[msvc::forceinline]] keeps the symbol where __forceinline drops it
2022 lto=ON: PARITY, [[msvc::forceinline]] keeps the symbol where __forceinline drops it
-----------------------------------------------

[1] https://gcc.gnu.org/onlinedocs/gcc/Common-Attributes.html#index-always_005finline
    @ceztko
    ceztko committed Sep 12, 2026
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