https://llvm.org/bugs/show_bug.cgi?id=23404
Bug ID: 23404
Summary: int32_t vs. int64_t vs. long ambiguity
Product: clang
Version: 3.6
Hardware: Macintosh
OS: All
Status: NEW
Severity: normal
Priority: P
Component: C++11
Assignee: [email protected]
Reporter: [email protected]
CC: [email protected], [email protected]
Classification: Unclassified
Consider the following program:
//--------------------------------------------------------------------
#include <cstdint>
#include <iostream>
void foo(std::int32_t) { std::cout << "int32_t\n"; }
void foo(std::int64_t) { std::cout << "int64_t\n"; }
int main()
{
static_assert(sizeof(123L) == 8, "long is not 64-bit");
foo(123L);
}
//--------------------------------------------------------------------
It produces (with a 64-bit target) the compiler error:
test.cc:11:5: error: call to 'foo' is ambiguous
I see no reason why it should be ambiguous. 123L is unambiguously a 64-bit
literal and should not match std::int32_t.
The literal value being small is not the reason for the error because the exact
same error happens with "foo(0x100000000L)" which shouldn't fit a std::int32_t,
and also with "foo(variable)" where 'variable' is of long type.
Note that "foo(123)" does not cause an error, instead compiling just fine (and
calling the std::int32_t version of the function). Obviously "foo(123LL)" does
not cause an error either. Only "foo(123L)" does.
The error can be circumvented by adding a new version of the function:
void foo(long) { std::cout << "long\n"; }
The problem with this is that I don't think it's a portable program anymore.
That's because if eg. std::int64_t happens to be typedeffed to 'long' in some
other compiler, it will cause a redefinition error. Indeed, if I added eg. this
function:
void foo(long long) { std::cout << "long long\n"; }
I get:
test.cc:7:6: error: redefinition of 'foo'
Is there a reason why a 64-bit 'long' value cannot unambiguously match
std::int64_t?
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