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<base href="https://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - int32_t vs. int64_t vs. long ambiguity"
href="https://llvm.org/bugs/show_bug.cgi?id=23404">23404</a>
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<th>Summary</th>
<td>int32_t vs. int64_t vs. long ambiguity
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>3.6
</td>
</tr>
<tr>
<th>Hardware</th>
<td>Macintosh
</td>
</tr>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>C++11
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>warp@iki.fi
</td>
</tr>
<tr>
<th>CC</th>
<td>dgregor@apple.com, llvmbugs@cs.uiuc.edu
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</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>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?</pre>
</div>
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