Adding '#define _USE_MATH_DEFINES' to make M_PI declared in Intel and MSVC compilers#3238
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M_PI is undeclared in Intel and MSVC compilers. To make it declared in these compilers '#define _USE_MATH_DEFINES' must be added before '#include <cmath>'.
M_PI is undeclared in Intel and MSVC compilers. To make it declared in these compilers '#define _USE_MATH_DEFINES' must be added before '#include <cmath>'.
M_PI is undeclared in Intel and MSVC compilers. To make it declared in these compilers '#define _USE_MATH_DEFINES' must be added before '#include <cmath>'.
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You're welcome @paulromano. |
apingegno
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… MSVC compilers (openmc-dev#3238) Co-authored-by: Paul Romano <paul.k.romano@gmail.com>
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In mesh.cpp and plot.cpp the definition sits below the first include, which transitively pulls in <cmath>: mesh.cpp:1 -> openmc/mesh.h -> openmc/position.h:4 -> <cmath> plot.cpp:1 -> openmc/plot.h:4 -> <cmath> <math.h> is #pragma once, so defining the macro afterwards cannot take effect and M_PI stays undeclared. Moving the definition above the first include restores the intent of openmc-dev#3238. In mesh.cpp the definition was also splitting the include block in two, which let the two halves stay individually sorted; moving it merges them and clang-format sorts the result. external/quartic_solver.cpp is unaffected: only <algorithm> precedes the definition there.
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In mesh.cpp and plot.cpp the definition sits below the first include, which transitively pulls in <cmath>: mesh.cpp:1 -> openmc/mesh.h -> openmc/position.h:4 -> <cmath> plot.cpp:1 -> openmc/plot.h:4 -> <cmath> Once math.h has been processed its include guard is set, so defining the macro afterwards cannot bring M_PI into scope. Measured with MinGW-w64 GCC 14.2.0 on Windows 11, compiling each file with the project's flags and no external -D_USE_MATH_DEFINES: before: mesh.cpp 2 errors, plot.cpp 1 error (M_PI was not declared) after: both compile There the macro matters because -std=c++17 defines __STRICT_ANSI__, which hides M_PI in the MinGW headers unless _USE_MATH_DEFINES is set. openmc-dev#3238 added these definitions for Intel and MSVC. I have no Intel or MSVC toolchain, so whether they are affected is untested here and worth confirming. In mesh.cpp the definition was also splitting the include block in two, which let the two halves stay individually sorted; moving it merges them and clang-format sorts the result. external/quartic_solver.cpp is unaffected: only <algorithm> precedes the definition there, and it compiles as-is.
lzpel
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openmc-dev#3238 added _USE_MATH_DEFINES to mesh.cpp, plot.cpp and quartic_solver.cpp so that M_PI would be declared on Intel and MSVC. In all three the definition sits below an include that has already pulled in <cmath>, and once math.h has been processed its include guard is set, so the definition never takes effect. mesh.cpp:1 -> openmc/mesh.h -> openmc/position.h:4 -> <cmath> plot.cpp:1 -> openmc/plot.h:4 -> <cmath> quartic_solver.cpp:1 -> <algorithm> -> <cmath> (MSVC) Measured with MSVC 19.51.36248 (VS 2026) and MinGW-w64 GCC 14.2.0, compiling each file with no external -D_USE_MATH_DEFINES: MSVC before MSVC after MinGW before MinGW after mesh.cpp 2 errors ok 2 errors ok plot.cpp 1 error ok 1 error ok quartic_solver.cpp 3 errors ok ok ok quartic_solver.cpp is where the two toolchains differ: MSVC's <algorithm> reaches math.h transitively, libstdc++'s does not. Which header first reaches math.h is implementation-defined, so the only position that is safe everywhere is above every include. mesh.cpp and plot.cpp therefore drop the macro entirely and use the PI constant already in constants.h, which both files already include and which is bit-identical to M_PI. quartic_solver.cpp is vendored third-party code in namespace oqs, so it keeps M_PI and just moves the definition to the top. In mesh.cpp the definition was also splitting the include block in two, which let the two halves stay individually sorted; removing it merges them and clang-format sorts the result.
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M_PIused inmesh.cpp,plot.cpp, andquartic_solver.cppis undeclared in Intel and MSVC compilers. To make it declared in these compilers#define _USE_MATH_DEFINESmust be added before#include <cmath>.