Mixing
C++ class constructors qualified as __attribute__((pure)) or __attribute__((const))
Can and should C++ class constructors be declared __attribute__((pure)) if they only can reach data via its parameters? And in which cases should they be qualified as __attribute__((const))?
c++ attributes pure-function
asked Nov 19 '18 at 13:06
Nordlöw
5,33934183
add a comment |
Can and should C++ class constructors be declared __attribute__((pure)) if they only can reach data via its parameters? And in which cases should they be qualified as __attribute__((const))?
c++ attributes pure-function
asked Nov 19 '18 at 13:06
Nordlöw
5,33934183
Err, what's the point? When will an average well-formed program going to invoke a c'tor for the same object twice?
– StoryTeller
Nov 19 '18 at 13:09
Ahh, I didn't think of the fact that it creates/allocates a new instance. I guess it's not relevant to qualify constructors then.
– Nordlöw
Nov 19 '18 at 13:11
add a comment |
Can and should C++ class constructors be declared __attribute__((pure)) if they only can reach data via its parameters? And in which cases should they be qualified as __attribute__((const))?
c++ attributes pure-function
asked Nov 19 '18 at 13:06
Nordlöw
5,33934183
Can and should C++ class constructors be declared __attribute__((pure)) if they only can reach data via its parameters? And in which cases should they be qualified as __attribute__((const))?
c++ attributes pure-function
c++ attributes pure-function
asked Nov 19 '18 at 13:06
Nordlöw
5,33934183
asked Nov 19 '18 at 13:06
Nordlöw
5,33934183
asked Nov 19 '18 at 13:06
Nordlöw
5,33934183
asked Nov 19 '18 at 13:06
Nordlöw
5,33934183
asked Nov 19 '18 at 13:06
Nordlöw
5,33934183
5,33934183
Err, what's the point? When will an average well-formed program going to invoke a c'tor for the same object twice?
– StoryTeller
Nov 19 '18 at 13:09
Ahh, I didn't think of the fact that it creates/allocates a new instance. I guess it's not relevant to qualify constructors then.
– Nordlöw
Nov 19 '18 at 13:11
add a comment |
Err, what's the point? When will an average well-formed program going to invoke a c'tor for the same object twice?
– StoryTeller
Nov 19 '18 at 13:09
Ahh, I didn't think of the fact that it creates/allocates a new instance. I guess it's not relevant to qualify constructors then.
– Nordlöw
Nov 19 '18 at 13:11
Err, what's the point? When will an average well-formed program going to invoke a c'tor for the same object twice?
– StoryTeller
Nov 19 '18 at 13:09
Err, what's the point? When will an average well-formed program going to invoke a c'tor for the same object twice?
– StoryTeller
Nov 19 '18 at 13:09
Ahh, I didn't think of the fact that it creates/allocates a new instance. I guess it's not relevant to qualify constructors then.
– Nordlöw
Nov 19 '18 at 13:11
Ahh, I didn't think of the fact that it creates/allocates a new instance. I guess it's not relevant to qualify constructors then.
– Nordlöw
Nov 19 '18 at 13:11
add a comment |
1 Answer
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oldest
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GCC warns when you qualify constructors as pure or const. This is because a constructor does not return anything (returns void) and it does not make much sense to have a pure or const attributes on such functions.
See godbolt demo here.
<source>:3:30: warning: 'pure' attribute on function returning 'void' [-Wattributes]
A() __attribute__((pure));
^
<source>:8:31: warning: 'const' attribute on function returning 'void' [-Wattributes]
B() __attribute__((const)); ^
From GCC documentation:
const
...
Because a const function cannot have any side effects it does not make sense for such a function to return void. Declaring such a function is diagnosed.
pure
...
Because a pure function cannot have any side effects it does not make sense for such a function to return void. Declaring such a function is diagnosed.
answered Nov 19 '18 at 13:34
P.W
10.9k3742
add a comment |
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1 Answer
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GCC warns when you qualify constructors as pure or const. This is because a constructor does not return anything (returns void) and it does not make much sense to have a pure or const attributes on such functions.
See godbolt demo here.
<source>:3:30: warning: 'pure' attribute on function returning 'void' [-Wattributes]
A() __attribute__((pure));
^
<source>:8:31: warning: 'const' attribute on function returning 'void' [-Wattributes]
B() __attribute__((const)); ^
From GCC documentation:
const
...
Because a const function cannot have any side effects it does not make sense for such a function to return void. Declaring such a function is diagnosed.
pure
...
Because a pure function cannot have any side effects it does not make sense for such a function to return void. Declaring such a function is diagnosed.
answered Nov 19 '18 at 13:34
P.W
10.9k3742
add a comment |
GCC warns when you qualify constructors as pure or const. This is because a constructor does not return anything (returns void) and it does not make much sense to have a pure or const attributes on such functions.
See godbolt demo here.
<source>:3:30: warning: 'pure' attribute on function returning 'void' [-Wattributes]
A() __attribute__((pure));
^
<source>:8:31: warning: 'const' attribute on function returning 'void' [-Wattributes]
B() __attribute__((const)); ^
From GCC documentation:
const
...
Because a const function cannot have any side effects it does not make sense for such a function to return void. Declaring such a function is diagnosed.
pure
...
Because a pure function cannot have any side effects it does not make sense for such a function to return void. Declaring such a function is diagnosed.
answered Nov 19 '18 at 13:34
P.W
10.9k3742
add a comment |
GCC warns when you qualify constructors as pure or const. This is because a constructor does not return anything (returns void) and it does not make much sense to have a pure or const attributes on such functions.
See godbolt demo here.
<source>:3:30: warning: 'pure' attribute on function returning 'void' [-Wattributes]
A() __attribute__((pure));
^
<source>:8:31: warning: 'const' attribute on function returning 'void' [-Wattributes]
B() __attribute__((const)); ^
From GCC documentation:
const
...
Because a const function cannot have any side effects it does not make sense for such a function to return void. Declaring such a function is diagnosed.
pure
...
Because a pure function cannot have any side effects it does not make sense for such a function to return void. Declaring such a function is diagnosed.
answered Nov 19 '18 at 13:34
P.W
10.9k3742
GCC warns when you qualify constructors as pure or const. This is because a constructor does not return anything (returns void) and it does not make much sense to have a pure or const attributes on such functions.
See godbolt demo here.
<source>:3:30: warning: 'pure' attribute on function returning 'void' [-Wattributes]
A() __attribute__((pure));
^
<source>:8:31: warning: 'const' attribute on function returning 'void' [-Wattributes]
B() __attribute__((const)); ^
From GCC documentation:
const
...
Because a const function cannot have any side effects it does not make sense for such a function to return void. Declaring such a function is diagnosed.
pure
...
Because a pure function cannot have any side effects it does not make sense for such a function to return void. Declaring such a function is diagnosed.
answered Nov 19 '18 at 13:34
P.W
10.9k3742
answered Nov 19 '18 at 13:34
P.W
10.9k3742
answered Nov 19 '18 at 13:34
P.W
10.9k3742
answered Nov 19 '18 at 13:34
P.W
10.9k3742
10.9k3742
add a comment |
add a comment |
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Err, what's the point? When will an average well-formed program going to invoke a c'tor for the same object twice?
– StoryTeller
Nov 19 '18 at 13:09
Ahh, I didn't think of the fact that it creates/allocates a new instance. I guess it's not relevant to qualify constructors then.
– Nordlöw
Nov 19 '18 at 13:11