Is &array[0]==(void*)&array guaranteed to be true? [duplicate]
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why cant we pass &array to function where &array[0] is possible
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Is a pointer to an arbitrary array equal to a pointer to the array's first element after cast to void*, and independently of the compiler?
I need a template function that takes a pointer to array[0] and gives a reference to the array. The code below does the job (at least in gcc and clang), and I would like to know if this is a legal C++ code.
My doubts are caused by the fact, that without cast to void* the code that uses the template would not compile (error message: ``static_cast from 'int ' to 'int ()[10]' is not allowed").
Thanks in advance. Here is the code:
template <std::size_t n, typename T>
inline T (& p2a( T * ptr))[n]
{
return *static_cast<T(*)[n]>( static_cast<void*>(ptr) );
}
c++ arrays
asked Nov 11 at 17:06
user10636819
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Nov 11 at 17:26
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
add a comment |
up vote
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This question already has an answer here:
why cant we pass &array to function where &array[0] is possible
6 answers
Is a pointer to an arbitrary array equal to a pointer to the array's first element after cast to void*, and independently of the compiler?
I need a template function that takes a pointer to array[0] and gives a reference to the array. The code below does the job (at least in gcc and clang), and I would like to know if this is a legal C++ code.
My doubts are caused by the fact, that without cast to void* the code that uses the template would not compile (error message: ``static_cast from 'int ' to 'int ()[10]' is not allowed").
Thanks in advance. Here is the code:
template <std::size_t n, typename T>
inline T (& p2a( T * ptr))[n]
{
return *static_cast<T(*)[n]>( static_cast<void*>(ptr) );
}
c++ arrays
asked Nov 11 at 17:06
user10636819
472
marked as duplicate by πάντα ῥεῖ c++
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Nov 11 at 17:26
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
Interesting question. I don't think the standard guarantees there must be no padding at the beginning of an array, but it'd be weird if there were.
– PSkocik
Nov 11 at 17:24
Related: stackoverflow.com/questions/47522295/…
– PSkocik
Nov 11 at 17:27
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up vote
1
down vote
favorite
up vote
1
down vote
favorite
This question already has an answer here:
why cant we pass &array to function where &array[0] is possible
6 answers
Is a pointer to an arbitrary array equal to a pointer to the array's first element after cast to void*, and independently of the compiler?
I need a template function that takes a pointer to array[0] and gives a reference to the array. The code below does the job (at least in gcc and clang), and I would like to know if this is a legal C++ code.
My doubts are caused by the fact, that without cast to void* the code that uses the template would not compile (error message: ``static_cast from 'int ' to 'int ()[10]' is not allowed").
Thanks in advance. Here is the code:
template <std::size_t n, typename T>
inline T (& p2a( T * ptr))[n]
{
return *static_cast<T(*)[n]>( static_cast<void*>(ptr) );
}
c++ arrays
asked Nov 11 at 17:06
user10636819
472
This question already has an answer here:
why cant we pass &array to function where &array[0] is possible
6 answers
Is a pointer to an arbitrary array equal to a pointer to the array's first element after cast to void*, and independently of the compiler?
I need a template function that takes a pointer to array[0] and gives a reference to the array. The code below does the job (at least in gcc and clang), and I would like to know if this is a legal C++ code.
My doubts are caused by the fact, that without cast to void* the code that uses the template would not compile (error message: ``static_cast from 'int ' to 'int ()[10]' is not allowed").
Thanks in advance. Here is the code:
template <std::size_t n, typename T>
inline T (& p2a( T * ptr))[n]
{
return *static_cast<T(*)[n]>( static_cast<void*>(ptr) );
}
This question already has an answer here:
why cant we pass &array to function where &array[0] is possible
6 answers
c++ arrays
c++ arrays
asked Nov 11 at 17:06
user10636819
472
asked Nov 11 at 17:06
user10636819
472
asked Nov 11 at 17:06
user10636819
472
asked Nov 11 at 17:06
user10636819
472
asked Nov 11 at 17:06
user10636819
472
472
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Nov 11 at 17:26
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
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Nov 11 at 17:26
This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.
Interesting question. I don't think the standard guarantees there must be no padding at the beginning of an array, but it'd be weird if there were.
– PSkocik
Nov 11 at 17:24
Related: stackoverflow.com/questions/47522295/…
– PSkocik
Nov 11 at 17:27
add a comment |
Interesting question. I don't think the standard guarantees there must be no padding at the beginning of an array, but it'd be weird if there were.
– PSkocik
Nov 11 at 17:24
Related: stackoverflow.com/questions/47522295/…
– PSkocik
Nov 11 at 17:27
Interesting question. I don't think the standard guarantees there must be no padding at the beginning of an array, but it'd be weird if there were.
– PSkocik
Nov 11 at 17:24
Interesting question. I don't think the standard guarantees there must be no padding at the beginning of an array, but it'd be weird if there were.
– PSkocik
Nov 11 at 17:24
Related: stackoverflow.com/questions/47522295/…
– PSkocik
Nov 11 at 17:27
Related: stackoverflow.com/questions/47522295/…
– PSkocik
Nov 11 at 17:27
add a comment |
1 Answer
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Yes, the address of an array is the same as the address of the array's first element (i.e., there is no padding at the beginning of an array) and a cast to void* doesn't change the address, so your code does the right thing. However, it is more straightforward to write it as follows:
template <std::size_t n, typename T>
inline auto p2a(T* ptr) {
return reinterpret_cast<T(&)[N]>(*ptr);
}
answered Nov 11 at 17:23
Brian
63.7k794179
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1 Answer
1
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oldest
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1 Answer
1
active
oldest
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active
oldest
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active
oldest
votes
up vote
0
down vote
Yes, the address of an array is the same as the address of the array's first element (i.e., there is no padding at the beginning of an array) and a cast to void* doesn't change the address, so your code does the right thing. However, it is more straightforward to write it as follows:
template <std::size_t n, typename T>
inline auto p2a(T* ptr) {
return reinterpret_cast<T(&)[N]>(*ptr);
}
answered Nov 11 at 17:23
Brian
63.7k794179
add a comment |
up vote
0
down vote
Yes, the address of an array is the same as the address of the array's first element (i.e., there is no padding at the beginning of an array) and a cast to void* doesn't change the address, so your code does the right thing. However, it is more straightforward to write it as follows:
template <std::size_t n, typename T>
inline auto p2a(T* ptr) {
return reinterpret_cast<T(&)[N]>(*ptr);
}
answered Nov 11 at 17:23
Brian
63.7k794179
add a comment |
up vote
0
down vote
up vote
0
down vote
Yes, the address of an array is the same as the address of the array's first element (i.e., there is no padding at the beginning of an array) and a cast to void* doesn't change the address, so your code does the right thing. However, it is more straightforward to write it as follows:
template <std::size_t n, typename T>
inline auto p2a(T* ptr) {
return reinterpret_cast<T(&)[N]>(*ptr);
}
answered Nov 11 at 17:23
Brian
63.7k794179
Yes, the address of an array is the same as the address of the array's first element (i.e., there is no padding at the beginning of an array) and a cast to void* doesn't change the address, so your code does the right thing. However, it is more straightforward to write it as follows:
template <std::size_t n, typename T>
inline auto p2a(T* ptr) {
return reinterpret_cast<T(&)[N]>(*ptr);
}
answered Nov 11 at 17:23
Brian
63.7k794179
answered Nov 11 at 17:23
Brian
63.7k794179
answered Nov 11 at 17:23
Brian
63.7k794179
answered Nov 11 at 17:23
Brian
63.7k794179
63.7k794179
add a comment |
add a comment |
Interesting question. I don't think the standard guarantees there must be no padding at the beginning of an array, but it'd be weird if there were.
– PSkocik
Nov 11 at 17:24
Related: stackoverflow.com/questions/47522295/…
– PSkocik
Nov 11 at 17:27