Fix "Unknown CMake command "check_symbol_exists"."

[TheSCREWEDSoftware]

Unsure if this is the proper fix to this but for me is what worked.

[Ovahlord]

I can't reproduce the error. What cmake version do you use and how did you reproduce it?

[TheSCREWEDSoftware]

CMake 4.2.2

Configure, choose VS22 (VS26 not supported) and during configuration it threw the error (same as the one in the commit message)

Selecting Windows SDK version 10.0.26100.0 to target Windows 10.0.26200.
The C compiler identification is MSVC 19.44.35222.0
The CXX compiler identification is MSVC 19.44.35222.0
Detecting C compiler ABI info
Detecting C compiler ABI info - done
Check for working C compiler: C:/Program Files/Microsoft Visual Studio/2022/Community/VC/Tools/MSVC/14.44.35207/bin/Hostx64/x64/cl.exe - skipped
Detecting C compile features
Detecting C compile features - done
Detecting CXX compiler ABI info
Detecting CXX compiler ABI info - done
Check for working CXX compiler: C:/Program Files/Microsoft Visual Studio/2022/Community/VC/Tools/MSVC/14.44.35207/bin/Hostx64/x64/cl.exe - skipped
Detecting CXX compile features
Detecting CXX compile features - done
Detected 64-bit platform
MSVC: Minimum version required is 19.32, found 19.44.35222.0 - ok!
MSVC: 64-bit platform, enforced -D_WIN64 parameter
MSVC: Enabled increased number of sections in object files
MSVC: Overloaded standard names
MSVC: Disabled NON-SECURE warnings
MSVC: Disabled POSIX warnings
MSVC: Disabled generic compiletime warnings
Found MySQL:
Found Git: C:/Program Files/Git/cmd/git.exe (found suitable version "2.47.0.windows.2", minimum required is "1.7")
Found MySQL:   found components: binary
Found MySQL executable: C:/Program Files/MySQL/MySQL Workbench 8.0 CE/mysql.exe

* TrinityCore revision   : https://github.com/TheSCREWEDSoftware/TrinityCore-Cata/commit/716f480b79690150cd4c2ac351094f4d73417be5 2026-05-05 11:31:32 +0200 (master branch)

* Install core to        : C:/Program Files (x86)/TrinityCore

* Build world/auth       : Yes (default)
* Build with scripts     : Yes (static)
* Build map/vmap tools   : Yes (default)
* Build unit tests       : No (default)
* Unity build enabled    : No (default)
* Build core w/PCH       : Yes (default)
* Build scripts w/PCH    : Yes (default)
* Show compile-warnings  : No  (default)
* Use coreside debug     : No  (default)
* Show source tree       : Yes (hierarchical)
* Use GIT revision hash  : Yes (default)

Performing Test CMAKE_HAVE_LIBC_PTHREAD
Performing Test CMAKE_HAVE_LIBC_PTHREAD - Failed
Looking for pthread_create in pthreads
Looking for pthread_create in pthreads - not found
Looking for pthread_create in pthread
Looking for pthread_create in pthread - not found
Found Threads: TRUE
Boost toolset is unknown (compiler MSVC 19.44.35222.0)
Boost toolset is unknown (compiler MSVC 19.44.35222.0)
Boost toolset is unknown (compiler MSVC 19.44.35222.0)
Boost toolset is unknown (compiler MSVC 19.44.35222.0)
Boost toolset is unknown (compiler MSVC 19.44.35222.0)
Boost toolset is unknown (compiler MSVC 19.44.35222.0)
Boost toolset is unknown (compiler MSVC 19.44.35222.0)
Boost toolset is unknown (compiler MSVC 19.44.35222.0)
CMake Error at dep/fmt/CMakeLists.txt:18 (check_symbol_exists):
  Unknown CMake command "check_symbol_exists".

Configuring incomplete, errors occurred!

Edit: The original post at that I found the solution https://techoverflow.net/2019/06/20/how-to-fix-unknown-cmake-command-check_symbol_exists/

And CMake documentation does suggest it on the top before it's ran https://cmake.org/cmake/help/latest/module/CheckSymbolExists.html

[Shauren]

I can't reproduce the error. What cmake version do you use and how did you reproduce it?

you are on linux, jemalloc's cmakelists pulls in CheckSymbolExists for you

[SirFerMoX]

Problem: The include(CheckSymbolExists) directive was misplaced. It was sitting after the closing parenthesis ) of the FMT_HEADERS list (line 36), causing CMake to treat it as a stray statement that was never executed before check_symbol_exists was called on lines 18/20. This resulted in CMake not recognizing the command and throwing an error.

Fix: Moved include(CheckSymbolExists) to the top of the file, before any call to check_symbol_exists, so the module is properly loaded before it is used.

I am using Cmake 4.3.1 in windows and solution fixed the issue for me.