# Help with try\_run() and CMAKE\_FLAGS

**URL:** <https://discourse.cmake.org/t/help-with-try-run-and-cmake-flags/2636>\
**Category:** Code\
**Created:** [January 26, 2021, 2:00pm UTC](https://discourse.cmake.org/t/help-with-try-run-and-cmake-flags/2636 "2021-01-26T14:00:38Z")\
**Posts on this page:** 4\
**Page:** 1

<div class="post-metadata">

**Author:** ![mathomp4](https://discourse.cmake.org/user_avatar/discourse.cmake.org/mathomp4/32/176_2.png) [@mathomp4](https://discourse.cmake.org/u/mathomp4)\
**Post date:** [January 26, 2021, 2:00pm UTC](https://discourse.cmake.org/t/help-with-try-run-and-cmake-flags/2636/1 "2021-01-26T14:00:38Z")

</div>

All,

I’m trying to figure out how to test if a compiler flag _runs_ on a processor. The issue is that I’m porting some code from Intel chips to AMD Rome chips and I’ve found that if I compile (using Intel Fortran) with `-xCORE-AVX2`, code will compile fine on the Rome chips, but not run:

```console
$ cat bobo.F90
program test
   real :: x
end program test
$ ifort -xCORE-AVX2 bobo.F90
$ echo $?
0
$ ./a.out

Please verify that both the operating system and the processor support Intel(R) X87, CMOV, MMX, FXSAVE, SSE, SSE2, SSE3, SSSE3, SSE4_1, SSE4_2, MOVBE, POPCNT, AVX, F16C, FMA, BMI, LZCNT and AVX2 instructions.

$ echo $?
1

```

Our CMake files for this project have assume “If Intel Fortran, use this flag” but now I need to be more subtle. So to test some things, I made up a simple CMake tester thinking this would be a way to test:

```cmake
cmake_minimum_required (VERSION 3.17)

project(testflag Fortran)

set(XCORE_FLAG "-xCORE-AVX2")

try_run(
   RUN_RESULT_VAR COMPILE_RESULT_VAR
   ${CMAKE_CURRENT_BINARY_DIR}/test ${CMAKE_CURRENT_LIST_DIR}/bobo.F90
   CMAKE_FLAGS "-DCMAKE_Fortran_FLAGS:STRING=${XCORE_FLAG}"
   COMPILE_OUTPUT_VARIABLE COMPILE_OUTPUT
   RUN_OUTPUT_VARIABLE RUN_OUTPUT
   )

message("COMPILE_RESULT_VAR = ${COMPILE_RESULT_VAR}")
message("COMPILE_OUTPUT = ${COMPILE_OUTPUT}")
message("RUN_RESULT_VAR = ${RUN_RESULT_VAR}")
message("RUN_OUTPUT = ${RUN_OUTPUT}")

```

But when I run:

```console
...
COMPILE_RESULT_VAR = TRUE
COMPILE_OUTPUT = Change Dir: /home3/mathomp4/RomeTest/CMakeTest/build/test/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/gmake cmTC_cefe8/fast && gmake: Warning: File 'Makefile' has modification time 0.0021 s in the future
/usr/bin/gmake -f CMakeFiles/cmTC_cefe8.dir/build.make CMakeFiles/cmTC_cefe8.dir/build
gmake[1]: Entering directory '/home3/mathomp4/RomeTest/CMakeTest/build/test/CMakeFiles/CMakeTmp'
Building Fortran object CMakeFiles/cmTC_cefe8.dir/bobo.F90.o
/nasa/intel/Compiler/2020.4.304/compilers_and_libraries_2020.4.304/linux/bin/intel64/ifort -c /home3/mathomp4/RomeTest/CMakeTest/bobo.F90 -o CMakeFiles/cmTC_cefe8.dir/bobo.F90.o
Linking Fortran executable cmTC_cefe8
/nobackupp16/gmao_SIteam/cmake/cmake-3.17.1/bin/cmake -E cmake_link_script CMakeFiles/cmTC_cefe8.dir/link.txt --verbose=1
/nasa/intel/Compiler/2020.4.304/compilers_and_libraries_2020.4.304/linux/bin/intel64/ifort CMakeFiles/cmTC_cefe8.dir/bobo.F90.o -o cmTC_cefe8
gmake[1]: Leaving directory '/home3/mathomp4/RomeTest/CMakeTest/build/test/CMakeFiles/CMakeTmp'
gmake: warning: Clock skew detected. Your build may be incomplete.

RUN_RESULT_VAR = 0
RUN_OUTPUT =
...

```

So the `-xCORE-AVX2` flag was never passed in and it passed. After reading internet a bit I tried this:

```cmake
try_run(
   RUN_RESULT_VAR COMPILE_RESULT_VAR
   ${CMAKE_CURRENT_BINARY_DIR}/test ${CMAKE_CURRENT_LIST_DIR}/bobo.F90
   COMPILE_DEFINITIONS "${XCORE_FLAG}"
   COMPILE_OUTPUT_VARIABLE COMPILE_OUTPUT
   RUN_OUTPUT_VARIABLE RUN_OUTPUT
   )

```

where I “hijacked” `COMPILE_DEFINITIONS` and:

```console
COMPILE_RESULT_VAR = TRUE
COMPILE_OUTPUT = Change Dir: /home3/mathomp4/RomeTest/CMakeTest/build/test/CMakeFiles/CMakeTmp

Run Build Command(s):/usr/bin/gmake cmTC_f89a4/fast && gmake: Warning: File 'Makefile' has modification time 0.0029 s in the future
/usr/bin/gmake -f CMakeFiles/cmTC_f89a4.dir/build.make CMakeFiles/cmTC_f89a4.dir/build
gmake[1]: Entering directory '/home3/mathomp4/RomeTest/CMakeTest/build/test/CMakeFiles/CMakeTmp'
gmake[1]: Warning: File 'CMakeFiles/cmTC_f89a4.dir/progress.make' has modification time 0.0043 s in the future
Building Fortran object CMakeFiles/cmTC_f89a4.dir/bobo.F90.o
/nasa/intel/Compiler/2020.4.304/compilers_and_libraries_2020.4.304/linux/bin/intel64/ifort -xCORE-AVX2 -c /home3/mathomp4/RomeTest/CMakeTest/bobo.F90 -o CMakeFiles/cmTC_f89a4.dir/bobo.F90.o
Linking Fortran executable cmTC_f89a4
/nobackupp16/gmao_SIteam/cmake/cmake-3.17.1/bin/cmake -E cmake_link_script CMakeFiles/cmTC_f89a4.dir/link.txt --verbose=1
/nasa/intel/Compiler/2020.4.304/compilers_and_libraries_2020.4.304/linux/bin/intel64/ifort CMakeFiles/cmTC_f89a4.dir/bobo.F90.o -o cmTC_f89a4
gmake[1]: warning: Clock skew detected. Your build may be incomplete.
gmake[1]: Leaving directory '/home3/mathomp4/RomeTest/CMakeTest/build/test/CMakeFiles/CMakeTmp'
gmake: warning: Clock skew detected. Your build may be incomplete.

RUN_RESULT_VAR = 1
RUN_OUTPUT =
Please verify that both the operating system and the processor support Intel(R) X87, CMOV, MMX, FXSAVE, SSE, SSE2, SSE3, SSSE3, SSE4_1, SSE4_2, MOVBE, POPCNT, AVX, F16C, FMA, BMI, LZCNT and AVX2 instructions.

```

So, I can get it to do what I want (aka fail)…but only in a way that seems wrong to me. Obviously I did the wrong thing with `CMAKE_FLAGS` and misread:

> Specify flags of the form `-DVAR:TYPE=VALUE` to be passed to the `cmake` command-line used to drive the test build.

What is the right way to do this?

---

<div class="post-metadata">

**Author:** ![ben.boeckel](https://discourse.cmake.org/letter_avatar_proxy/v4/letter/b/ea5d25/32.png) [@ben.boeckel](https://discourse.cmake.org/u/ben.boeckel)\
**Post date:** [January 26, 2021, 2:26pm UTC](https://discourse.cmake.org/t/help-with-try-run-and-cmake-flags/2636/2 "2021-01-26T14:26:22Z")

</div>

@brad.king It seems that `try_run` could use with a `COMPILE_OPTIONS` argument?

---

<div class="post-metadata">

**Author:** ![brad.king](https://discourse.cmake.org/user_avatar/discourse.cmake.org/brad.king/32/11_2.png) [@brad.king](https://discourse.cmake.org/u/brad.king)\
**Post date:** [January 26, 2021, 2:37pm UTC](https://discourse.cmake.org/t/help-with-try-run-and-cmake-flags/2636/3 "2021-01-26T14:37:45Z")

</div>

One can use [CheckSourceRuns](https://cmake.org/cmake/help/latest/module/CheckSourceRuns.html) with the `CMAKE_REQUIRED_FLAGS` setting.

It is implemented with `try_run` using an undocumented `-DCOMPILE_DEFINITIONS=<flags>` entry in `CMAKE_FLAGS`. One can see in [the implementation](https://gitlab.kitware.com/cmake/cmake/-/blob/v3.19.3/Source/cmCoreTryCompile.cxx#L587) that the value of the `COMPILE_DEFINITIONS` variable gets appended to `CMAKE_<LANG>_FLAGS` in the generated test project.

---

<div class="post-metadata">

**Author:** ![mathomp4](https://discourse.cmake.org/user_avatar/discourse.cmake.org/mathomp4/32/176_2.png) [@mathomp4](https://discourse.cmake.org/u/mathomp4)\
**Post date:** [January 26, 2021, 3:07pm UTC](https://discourse.cmake.org/t/help-with-try-run-and-cmake-flags/2636/4 "2021-01-26T15:07:23Z")

</div>

@brad.king Ah. I didn’t know about `CheckSourceRuns`! I will stare at it and try it out. (Warning: I might be back here to ask “what did I break now?” 🙂)

Unfortunately, it might be a bit before I can require CMake 3.19 (supercomputing cluster modules move slowly!), but I suppose I can use the `try_run` hack on older CMake’s. Time to make a `macro()`.

(That is, unless there is a CMake way to figure out if I’m on AMD Rome instead of, say, an Intel Cascade Lake? I’m pretty sure there isn’t a simple built-in way to check “CMAKE\_CPU\_TYPE” or the like.)