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1.. title:: clang-tidy - readability-isolate-declaration2 3readability-isolate-declaration4===============================5 6Detects local variable declarations declaring more than one variable and7tries to refactor the code to one statement per declaration.8 9The automatic code-transformation will use the same indentation as the original10for every created statement and add a line break after each statement.11It keeps the order of the variable declarations consistent, too.12 13.. code-block:: c++14 15 void f() {16 int * pointer = nullptr, value = 42, * const const_ptr = &value;17 // This declaration will be diagnosed and transformed into:18 // int * pointer = nullptr;19 // int value = 42;20 // int * const const_ptr = &value;21 }22 23 24The check excludes places where it is necessary or common to declare25multiple variables in one statement and there is no other way supported in the26language. Please note that structured bindings are not considered.27 28.. code-block:: c++29 30 // It is not possible to transform this declaration and doing the declaration31 // before the loop will increase the scope of the variable 'Begin' and 'End'32 // which is undesirable.33 for (int Begin = 0, End = 100; Begin < End; ++Begin);34 if (int Begin = 42, Result = some_function(Begin); Begin == Result);35 36 // It is not possible to transform this declaration because the result is37 // not functionality preserving as 'j' and 'k' would not be part of the38 // 'if' statement anymore.39 if (SomeCondition())40 int i = 42, j = 43, k = function(i,j);41 42 43Limitations44-----------45 46Global variables and member variables are excluded.47 48The check currently does not support the automatic transformation of49member-pointer-types.50 51.. code-block:: c++52 53 struct S {54 int a;55 const int b;56 void f() {}57 };58 59 void f() {60 // Only a diagnostic message is emitted61 int S::*p = &S::a, S::*const q = &S::a;62 }63 64Furthermore, the transformation is very cautious when it detects various kinds65of macros or preprocessor directives in the range of the statement. In this66case the transformation will not happen to avoid unexpected side-effects due to67macros.68 69.. code-block:: c++70 71 #define NULL 072 #define MY_NICE_TYPE int **73 #define VAR_NAME(name) name##__LINE__74 #define A_BUNCH_OF_VARIABLES int m1 = 42, m2 = 43, m3 = 44;75 76 void macros() {77 int *p1 = NULL, *p2 = NULL;78 // Will be transformed to79 // int *p1 = NULL;80 // int *p2 = NULL;81 82 MY_NICE_TYPE p3, v1, v2;83 // Won't be transformed, but a diagnostic is emitted.84 85 int VAR_NAME(v3),86 VAR_NAME(v4),87 VAR_NAME(v5);88 // Won't be transformed, but a diagnostic is emitted.89 90 A_BUNCH_OF_VARIABLES91 // Won't be transformed, but a diagnostic is emitted.92 93 int Unconditional,94 #if CONFIGURATION95 IfConfigured = 42,96 #else97 IfConfigured = 0;98 #endif99 // Won't be transformed, but a diagnostic is emitted.100 }101