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Merge topic 'tutorial-cmath'

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5c84eca210 Tutorial: Simplify logic checking for cmath functions

Acked-by: Kitware Robot <kwrobot@kitware.com>
Acked-by: buildbot <buildbot@kitware.com>
Merge-request: !7314
This commit is contained in:
Brad King
2022-06-02 13:20:52 +00:00
committed by Kitware Robot
parent 4c9aa6c425 5c84eca210
commit dbb6e04b5f
3 changed files with 19 additions and 19 deletions
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8
Help/guide/tutorial/Adding System Introspection.rst
View File

@@ -9,17 +9,15 @@ tutorial assume that they are not common.
If the platform has ``log`` and ``exp`` then we will use them to compute the
square root in the ``mysqrt`` function. We first test for the availability of
these functions using the :module:`CheckSymbolExists` module in
``MathFunctions/CMakeLists.txt``. On some platforms, we will need to link to
the ``m`` library. If ``log`` and ``exp`` are not initially found, require the
``m`` library and try again.
these functions using the :module:`CheckCXXSourceCompiles` module in
``MathFunctions/CMakeLists.txt``.
Add the checks for ``log`` and ``exp`` to ``MathFunctions/CMakeLists.txt``,
after the call to :command:`target_include_directories`:
.. literalinclude:: Step6/MathFunctions/CMakeLists.txt
:caption: MathFunctions/CMakeLists.txt
:name: MathFunctions/CMakeLists.txt-check_symbol_exists
:name: MathFunctions/CMakeLists.txt-check_cxx_source_compiles
:language: cmake
:start-after: # to find MathFunctions.h, while we don't.
:end-before: # add compile definitions

28
Help/guide/tutorial/Step6/MathFunctions/CMakeLists.txt
View File

@@ -7,19 +7,21 @@ target_include_directories(MathFunctions
)
# does this system provide the log and exp functions?
include(CheckSymbolExists)
check_symbol_exists(log "math.h" HAVE_LOG)
check_symbol_exists(exp "math.h" HAVE_EXP)
if(NOT (HAVE_LOG AND HAVE_EXP))
unset(HAVE_LOG CACHE)
unset(HAVE_EXP CACHE)
set(CMAKE_REQUIRED_LIBRARIES "m")
check_symbol_exists(log "math.h" HAVE_LOG)
check_symbol_exists(exp "math.h" HAVE_EXP)
if(HAVE_LOG AND HAVE_EXP)
target_link_libraries(MathFunctions PRIVATE m)
endif()
endif()
include(CheckCXXSourceCompiles)
check_cxx_source_compiles("
#include <cmath>
int main() {
std::log(1.0);
return 0;
}
" HAVE_LOG)
check_cxx_source_compiles("
#include <cmath>
int main() {
std::exp(1.0);
return 0;
}
" HAVE_EXP)
# add compile definitions
if(HAVE_LOG AND HAVE_EXP)

2
Help/guide/tutorial/Step6/MathFunctions/mysqrt.cxx
View File

@@ -12,7 +12,7 @@ double mysqrt(double x)
// if we have both log and exp then use them
#if defined(HAVE_LOG) && defined(HAVE_EXP)
double result = exp(log(x) * 0.5);
double result = std::exp(std::log(x) * 0.5);
std::cout << "Computing sqrt of " << x << " to be " << result
<< " using log and exp" << std::endl;
#else