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Consider the following C++11 code:
template <typename T>
class optional_ref {
public:
optional_ref() : ref_(nullptr) {}
optional_ref(const T& ref) : ref_(&ref) {}
bool has_value() const { return ref_ != nullptr; }
const T& value() const { return *ref_; }
private:
const T* ref_;
};
class stream_t {};
template <typename T, unsigned long N>
void copy(T(&destination)[N], optional_ref<const stream_t> stream = {}) // !!!
{ destination[0] = 1; }
This code compiles fine with g++; but - MSVC doesn't like it for some reason, giving the following errors regarding the line marked !!!:
error C2065: 'destination': undeclared identifier
error C2275: 'optional_ref<const stream_t>': expected an expression instead of a type
error C2146: syntax error: missing ')' before identifier 'stream'
error C2143: syntax error: missing ';' before '{'
error C2143: syntax error: missing ')' before ';'
error C2447: '{': missing function header (old-style formal list?)
error C2059: syntax error: ')'
error C2447: '{': missing function header (old-style formal list?)
It seems like it is having some trouble with the array-reference parameter. But - what is it actually complaining about?
I would appreciate some input from someone with more MSVC experience, who may be able to better decipher this sequence of errors.
Consider the following C++11 code:
template <typename T>
class optional_ref {
public:
optional_ref() : ref_(nullptr) {}
optional_ref(const T& ref) : ref_(&ref) {}
bool has_value() const { return ref_ != nullptr; }
const T& value() const { return *ref_; }
private:
const T* ref_;
};
class stream_t {};
template <typename T, unsigned long N>
void copy(T(&destination)[N], optional_ref<const stream_t> stream = {}) // !!!
{ destination[0] = 1; }
This code compiles fine with g++; but - MSVC doesn't like it for some reason, giving the following errors regarding the line marked !!!:
error C2065: 'destination': undeclared identifier
error C2275: 'optional_ref<const stream_t>': expected an expression instead of a type
error C2146: syntax error: missing ')' before identifier 'stream'
error C2143: syntax error: missing ';' before '{'
error C2143: syntax error: missing ')' before ';'
error C2447: '{': missing function header (old-style formal list?)
error C2059: syntax error: ')'
error C2447: '{': missing function header (old-style formal list?)
It seems like it is having some trouble with the array-reference parameter. But - what is it actually complaining about?
I would appreciate some input from someone with more MSVC experience, who may be able to better decipher this sequence of errors.
Share Improve this question edited Nov 17, 2024 at 21:55 einpoklum asked Nov 16, 2024 at 19:41 einpoklumeinpoklum 133k80 gold badges422 silver badges867 bronze badges2 Answers
Reset to default 3This looks like a MSVC bug, you can report it to Microsoft here. In the meantime, aliasing the array as another type works for me:
template <typename T, size_t N>
using dest_array = T[N];
// Function template
template <typename T, size_t N>
void copy(dest_array<T, N>& destination, span<T const> source, optional_ref<const stream_t> stream = {})
{
...
}
Link to Godbolt example to verify it works on latest MSVC: https://godbolt./z/nb76MdP4c. Thanks!
This seems to be an MSVC bug, which I have now filed as:
MSVC rejects syntax of reference to C array as a function parameter
Will update if/when it's fixed.
Credit to this answer from Anis Ladram, who suggested this as a compiler bug.
Consider the following C++11 code:
template <typename T>
class optional_ref {
public:
optional_ref() : ref_(nullptr) {}
optional_ref(const T& ref) : ref_(&ref) {}
bool has_value() const { return ref_ != nullptr; }
const T& value() const { return *ref_; }
private:
const T* ref_;
};
class stream_t {};
template <typename T, unsigned long N>
void copy(T(&destination)[N], optional_ref<const stream_t> stream = {}) // !!!
{ destination[0] = 1; }
This code compiles fine with g++; but - MSVC doesn't like it for some reason, giving the following errors regarding the line marked !!!:
error C2065: 'destination': undeclared identifier
error C2275: 'optional_ref<const stream_t>': expected an expression instead of a type
error C2146: syntax error: missing ')' before identifier 'stream'
error C2143: syntax error: missing ';' before '{'
error C2143: syntax error: missing ')' before ';'
error C2447: '{': missing function header (old-style formal list?)
error C2059: syntax error: ')'
error C2447: '{': missing function header (old-style formal list?)
It seems like it is having some trouble with the array-reference parameter. But - what is it actually complaining about?
I would appreciate some input from someone with more MSVC experience, who may be able to better decipher this sequence of errors.
Consider the following C++11 code:
template <typename T>
class optional_ref {
public:
optional_ref() : ref_(nullptr) {}
optional_ref(const T& ref) : ref_(&ref) {}
bool has_value() const { return ref_ != nullptr; }
const T& value() const { return *ref_; }
private:
const T* ref_;
};
class stream_t {};
template <typename T, unsigned long N>
void copy(T(&destination)[N], optional_ref<const stream_t> stream = {}) // !!!
{ destination[0] = 1; }
This code compiles fine with g++; but - MSVC doesn't like it for some reason, giving the following errors regarding the line marked !!!:
error C2065: 'destination': undeclared identifier
error C2275: 'optional_ref<const stream_t>': expected an expression instead of a type
error C2146: syntax error: missing ')' before identifier 'stream'
error C2143: syntax error: missing ';' before '{'
error C2143: syntax error: missing ')' before ';'
error C2447: '{': missing function header (old-style formal list?)
error C2059: syntax error: ')'
error C2447: '{': missing function header (old-style formal list?)
It seems like it is having some trouble with the array-reference parameter. But - what is it actually complaining about?
I would appreciate some input from someone with more MSVC experience, who may be able to better decipher this sequence of errors.
Share Improve this question edited Nov 17, 2024 at 21:55 einpoklum asked Nov 16, 2024 at 19:41 einpoklumeinpoklum 133k80 gold badges422 silver badges867 bronze badges2 Answers
Reset to default 3This looks like a MSVC bug, you can report it to Microsoft here. In the meantime, aliasing the array as another type works for me:
template <typename T, size_t N>
using dest_array = T[N];
// Function template
template <typename T, size_t N>
void copy(dest_array<T, N>& destination, span<T const> source, optional_ref<const stream_t> stream = {})
{
...
}
Link to Godbolt example to verify it works on latest MSVC: https://godbolt./z/nb76MdP4c. Thanks!
This seems to be an MSVC bug, which I have now filed as:
MSVC rejects syntax of reference to C array as a function parameter
Will update if/when it's fixed.
Credit to this answer from Anis Ladram, who suggested this as a compiler bug.
本文标签： arraysMSVC rejects the syntax of a line which GCC acceptsmakes weird complaintStack Overflow
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