krasin added a comment.
This change makes Clang hardly incompatible with MSVC++. Consider the following
program:
#include <stdio.h>
int main(void) {
const int kDelta = 10000001;
auto g = [kDelta](int i)
{
printf("%d\n", i % kDelta);
};
g(2);
}
Clang will warn about the unused lambda capture:
$ clang++ lala.cc -o lala -std=c++14 -Wall -Werror && ./lala
lala.cc:5:13: error: lambda capture 'kDelta' is not required to be captured
for use in an unevaluated context [-Werror,-Wunused-lambda-capture]
auto g = [kDelta](int i)
^
1 error generated.
It will compile without any warnings if I remove kDelta from the list of
captures:
#include <stdio.h>
int main(void) {
const int kDelta = 10000001;
auto g = [](int i)
{
printf("%d\n", i % kDelta);
};
g(2);
}
But then Microsoft C++ compiler will raise the error:
error C3493: 'kDelta' cannot be implicitly captured because no default
capture mode has been specified
At this point, I am unsure how can this be improved, but I feel that pointing
out this inconsistency might be useful.
For real world case, see https://codereview.chromium.org/2646553002/, where I
tried to fix unused lambda captures in V8, in particular, this failure:
https://build.chromium.org/p/tryserver.v8/builders/v8_win_rel_ng/builds/21172/steps/compile/logs/stdio
Repository:
rL LLVM
https://reviews.llvm.org/D28467
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