From 3995deaf76d0c988d315630ace46eb01dba37174 Mon Sep 17 00:00:00 2001
From: Dale Phurrough <dale@hidale.com>
Date: Sat, 28 Aug 2021 01:12:44 +0200
Subject: [PATCH] fix opencv/opencv#20544 nodiscard for msvc/gcc
- includes workaround for preprocessor non-compliance
- enable attribute syntax checking in msvc
---
cmake/OpenCVCompilerOptions.cmake | 3 ++
modules/core/include/opencv2/core/cvdef.h | 39 ++++++++++++--
modules/core/include/opencv2/core/mat.hpp | 62 +++++++++++-----------
modules/core/include/opencv2/core/matx.hpp | 14 ++---
4 files changed, 77 insertions(+), 41 deletions(-)
diff --git a/cmake/OpenCVCompilerOptions.cmake b/cmake/OpenCVCompilerOptions.cmake
index 303d4f451e..d444085ea3 100644
--- a/cmake/OpenCVCompilerOptions.cmake
+++ b/cmake/OpenCVCompilerOptions.cmake
@@ -400,6 +400,9 @@ if(MSVC)
endif()
endif()
+ # Enable [[attribute]] syntax checking to prevent silent failure: "attribute is ignored in this syntactic position"
+ add_extra_compiler_option("/w15240")
+
if(NOT ENABLE_NOISY_WARNINGS)
ocv_warnings_disable(CMAKE_CXX_FLAGS /wd4127) # conditional expression is constant
ocv_warnings_disable(CMAKE_CXX_FLAGS /wd4251) # class 'std::XXX' needs to have dll-interface to be used by clients of YYY
diff --git a/modules/core/include/opencv2/core/cvdef.h b/modules/core/include/opencv2/core/cvdef.h
index a4b560b4e1..6011b2a931 100644
--- a/modules/core/include/opencv2/core/cvdef.h
+++ b/modules/core/include/opencv2/core/cvdef.h
@@ -575,14 +575,47 @@ Cv64suf;
# endif
#endif
+/****************************************************************************************\
+* CV_NODISCARD_STD attribute (C++17) *
+* encourages the compiler to issue a warning if the return value is discarded *
+\****************************************************************************************/
+#ifndef CV_NODISCARD_STD
+# ifndef __has_cpp_attribute
+// workaround preprocessor non-compliance https://reviews.llvm.org/D57851
+# define __has_cpp_attribute(__x) 0
+# endif
+# if __has_cpp_attribute(nodiscard)
+# define CV_NODISCARD_STD [[nodiscard]]
+# elif __cplusplus >= 201703L
+// available when compiler is C++17 compliant
+# define CV_NODISCARD_STD [[nodiscard]]
+# elif defined(_MSC_VER) && _MSC_VER >= 1911 && _MSVC_LANG >= 201703L
+// available with VS2017 v15.3+ with /std:c++17 or higher; works on functions and classes
+# define CV_NODISCARD_STD [[nodiscard]]
+# elif defined(__GNUC__) && (((__GNUC__ * 100) + __GNUC_MINOR__) >= 700) && (__cplusplus >= 201103L)
+// available with GCC 7.0+; works on functions, works or silently fails on classes
+# define CV_NODISCARD_STD [[nodiscard]]
+# elif defined(__GNUC__) && (((__GNUC__ * 100) + __GNUC_MINOR__) >= 408) && (__cplusplus >= 201103L)
+// available with GCC 4.8+ but it usually does nothing and can fail noisily -- therefore not used
+// define CV_NODISCARD_STD [[gnu::warn_unused_result]]
+# endif
+#endif
+#ifndef CV_NODISCARD_STD
+# define CV_NODISCARD_STD /* nothing by default */
+#endif
+
/****************************************************************************************\
-* CV_NODISCARD attribute *
-* encourages the compiler to issue a warning if the return value is discarded (C++17) *
+* CV_NODISCARD attribute (deprecated, GCC only) *
+* DONT USE: use instead the standard CV_NODISCARD_STD macro above *
+* this legacy method silently fails to issue warning until some version *
+* after gcc 6.3.0. Yet with gcc 7+ you can use the above standard method *
+* which makes this method useless. Don't use it. *
+* @deprecated use instead CV_NODISCARD_STD *
\****************************************************************************************/
#ifndef CV_NODISCARD
# if defined(__GNUC__)
-# define CV_NODISCARD __attribute__((__warn_unused_result__)) // at least available with GCC 3.4
+# define CV_NODISCARD __attribute__((__warn_unused_result__))
# elif defined(__clang__) && defined(__has_attribute)
# if __has_attribute(__warn_unused_result__)
# define CV_NODISCARD __attribute__((__warn_unused_result__))
diff --git a/modules/core/include/opencv2/core/mat.hpp b/modules/core/include/opencv2/core/mat.hpp
index d0ce61e123..fdcb8fc817 100644
--- a/modules/core/include/opencv2/core/mat.hpp
+++ b/modules/core/include/opencv2/core/mat.hpp
@@ -1204,14 +1204,14 @@ public:
The method creates a square diagonal matrix from specified main diagonal.
@param d One-dimensional matrix that represents the main diagonal.
*/
- static Mat diag(const Mat& d);
+ CV_NODISCARD_STD static Mat diag(const Mat& d);
/** @brief Creates a full copy of the array and the underlying data.
The method creates a full copy of the array. The original step[] is not taken into account. So, the
array copy is a continuous array occupying total()*elemSize() bytes.
*/
- Mat clone() const CV_NODISCARD;
+ CV_NODISCARD_STD Mat clone() const;
/** @brief Copies the matrix to another one.
@@ -1375,20 +1375,20 @@ public:
@param cols Number of columns.
@param type Created matrix type.
*/
- static MatExpr zeros(int rows, int cols, int type);
+ CV_NODISCARD_STD static MatExpr zeros(int rows, int cols, int type);
/** @overload
@param size Alternative to the matrix size specification Size(cols, rows) .
@param type Created matrix type.
*/
- static MatExpr zeros(Size size, int type);
+ CV_NODISCARD_STD static MatExpr zeros(Size size, int type);
/** @overload
@param ndims Array dimensionality.
@param sz Array of integers specifying the array shape.
@param type Created matrix type.
*/
- static MatExpr zeros(int ndims, const int* sz, int type);
+ CV_NODISCARD_STD static MatExpr zeros(int ndims, const int* sz, int type);
/** @brief Returns an array of all 1's of the specified size and type.
@@ -1406,20 +1406,20 @@ public:
@param cols Number of columns.
@param type Created matrix type.
*/
- static MatExpr ones(int rows, int cols, int type);
+ CV_NODISCARD_STD static MatExpr ones(int rows, int cols, int type);
/** @overload
@param size Alternative to the matrix size specification Size(cols, rows) .
@param type Created matrix type.
*/
- static MatExpr ones(Size size, int type);
+ CV_NODISCARD_STD static MatExpr ones(Size size, int type);
/** @overload
@param ndims Array dimensionality.
@param sz Array of integers specifying the array shape.
@param type Created matrix type.
*/
- static MatExpr ones(int ndims, const int* sz, int type);
+ CV_NODISCARD_STD static MatExpr ones(int ndims, const int* sz, int type);
/** @brief Returns an identity matrix of the specified size and type.
@@ -1435,13 +1435,13 @@ public:
@param cols Number of columns.
@param type Created matrix type.
*/
- static MatExpr eye(int rows, int cols, int type);
+ CV_NODISCARD_STD static MatExpr eye(int rows, int cols, int type);
/** @overload
@param size Alternative matrix size specification as Size(cols, rows) .
@param type Created matrix type.
*/
- static MatExpr eye(Size size, int type);
+ CV_NODISCARD_STD static MatExpr eye(Size size, int type);
/** @brief Allocates new array data if needed.
@@ -2302,7 +2302,7 @@ public:
Mat_ row(int y) const;
Mat_ col(int x) const;
Mat_ diag(int d=0) const;
- Mat_ clone() const CV_NODISCARD;
+ CV_NODISCARD_STD Mat_ clone() const;
//! overridden forms of Mat::elemSize() etc.
size_t elemSize() const;
@@ -2315,14 +2315,14 @@ public:
size_t stepT(int i=0) const;
//! overridden forms of Mat::zeros() etc. Data type is omitted, of course
- static MatExpr zeros(int rows, int cols);
- static MatExpr zeros(Size size);
- static MatExpr zeros(int _ndims, const int* _sizes);
- static MatExpr ones(int rows, int cols);
- static MatExpr ones(Size size);
- static MatExpr ones(int _ndims, const int* _sizes);
- static MatExpr eye(int rows, int cols);
- static MatExpr eye(Size size);
+ CV_NODISCARD_STD static MatExpr zeros(int rows, int cols);
+ CV_NODISCARD_STD static MatExpr zeros(Size size);
+ CV_NODISCARD_STD static MatExpr zeros(int _ndims, const int* _sizes);
+ CV_NODISCARD_STD static MatExpr ones(int rows, int cols);
+ CV_NODISCARD_STD static MatExpr ones(Size size);
+ CV_NODISCARD_STD static MatExpr ones(int _ndims, const int* _sizes);
+ CV_NODISCARD_STD static MatExpr eye(int rows, int cols);
+ CV_NODISCARD_STD static MatExpr eye(Size size);
//! some more overridden methods
Mat_& adjustROI( int dtop, int dbottom, int dleft, int dright );
@@ -2469,10 +2469,10 @@ public:
//! <0 - a diagonal from the lower half)
UMat diag(int d=0) const;
//! constructs a square diagonal matrix which main diagonal is vector "d"
- static UMat diag(const UMat& d);
+ CV_NODISCARD_STD static UMat diag(const UMat& d);
//! returns deep copy of the matrix, i.e. the data is copied
- UMat clone() const CV_NODISCARD;
+ CV_NODISCARD_STD UMat clone() const;
//! copies the matrix content to "m".
// It calls m.create(this->size(), this->type()).
void copyTo( OutputArray m ) const;
@@ -2503,14 +2503,14 @@ public:
double dot(InputArray m) const;
//! Matlab-style matrix initialization
- static UMat zeros(int rows, int cols, int type);
- static UMat zeros(Size size, int type);
- static UMat zeros(int ndims, const int* sz, int type);
- static UMat ones(int rows, int cols, int type);
- static UMat ones(Size size, int type);
- static UMat ones(int ndims, const int* sz, int type);
- static UMat eye(int rows, int cols, int type);
- static UMat eye(Size size, int type);
+ CV_NODISCARD_STD static UMat zeros(int rows, int cols, int type);
+ CV_NODISCARD_STD static UMat zeros(Size size, int type);
+ CV_NODISCARD_STD static UMat zeros(int ndims, const int* sz, int type);
+ CV_NODISCARD_STD static UMat ones(int rows, int cols, int type);
+ CV_NODISCARD_STD static UMat ones(Size size, int type);
+ CV_NODISCARD_STD static UMat ones(int ndims, const int* sz, int type);
+ CV_NODISCARD_STD static UMat eye(int rows, int cols, int type);
+ CV_NODISCARD_STD static UMat eye(Size size, int type);
//! allocates new matrix data unless the matrix already has specified size and type.
// previous data is unreferenced if needed.
@@ -2767,7 +2767,7 @@ public:
SparseMat& operator = (const Mat& m);
//! creates full copy of the matrix
- SparseMat clone() const CV_NODISCARD;
+ CV_NODISCARD_STD SparseMat clone() const;
//! copies all the data to the destination matrix. All the previous content of m is erased
void copyTo( SparseMat& m ) const;
@@ -3004,7 +3004,7 @@ public:
SparseMat_& operator = (const Mat& m);
//! makes full copy of the matrix. All the elements are duplicated
- SparseMat_ clone() const CV_NODISCARD;
+ CV_NODISCARD_STD SparseMat_ clone() const;
//! equivalent to cv::SparseMat::create(dims, _sizes, DataType<_Tp>::type)
void create(int dims, const int* _sizes);
//! converts sparse matrix to the old-style CvSparseMat. All the elements are copied
diff --git a/modules/core/include/opencv2/core/matx.hpp b/modules/core/include/opencv2/core/matx.hpp
index 733f675192..f25c8bce57 100644
--- a/modules/core/include/opencv2/core/matx.hpp
+++ b/modules/core/include/opencv2/core/matx.hpp
@@ -146,22 +146,22 @@ public:
Matx(std::initializer_list<_Tp>); //!< initialize from an initializer list
#endif
- static Matx all(_Tp alpha);
- static Matx zeros();
- static Matx ones();
- static Matx eye();
- static Matx diag(const diag_type& d);
+ CV_NODISCARD_STD static Matx all(_Tp alpha);
+ CV_NODISCARD_STD static Matx zeros();
+ CV_NODISCARD_STD static Matx ones();
+ CV_NODISCARD_STD static Matx eye();
+ CV_NODISCARD_STD static Matx diag(const diag_type& d);
/** @brief Generates uniformly distributed random numbers
@param a Range boundary.
@param b The other range boundary (boundaries don't have to be ordered, the lower boundary is inclusive,
the upper one is exclusive).
*/
- static Matx randu(_Tp a, _Tp b);
+ CV_NODISCARD_STD static Matx randu(_Tp a, _Tp b);
/** @brief Generates normally distributed random numbers
@param a Mean value.
@param b Standard deviation.
*/
- static Matx randn(_Tp a, _Tp b);
+ CV_NODISCARD_STD static Matx randn(_Tp a, _Tp b);
//! dot product computed with the default precision
_Tp dot(const Matx<_Tp, m, n>& v) const;