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Fix: fmt::ostream cannot be moved while holding buffered data #2197 #2198

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merged 2 commits into from
Mar 30, 2021
Merged

Fix: fmt::ostream cannot be moved while holding buffered data #2197 #2198

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291b007
Add a test case: move ostream while holding data
vtta Mar 29, 2021
b77d2a8
Fix moving ostream while holding data
vtta Mar 29, 2021
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2 changes: 2 additions & 0 deletions include/fmt/os.h
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Original file line number Diff line number Diff line change
Expand Up @@ -396,8 +396,10 @@ class ostream final : private detail::buffer<char> {
ostream(ostream&& other)
: detail::buffer<char>(other.data(), other.size(), other.capacity()),
file_(std::move(other.file_)) {
other.clear();
other.set(nullptr, 0);
Comment on lines +399 to 400
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@vitaut vitaut Mar 29, 2021 •
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I wonder if this can be replaced with

other = detail::buffer<char>();

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@vtta vtta Mar 29, 2021 •
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It seems reasonable, but I prefer the consistency between set and clear.
Another issue is that creating an additional object in the ctor seems confusing.

}

~ostream() {
flush();
delete[] data();
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13 changes: 13 additions & 0 deletions test/os-test.cc
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Expand Up @@ -293,6 +293,19 @@ TEST(OStreamTest, Move) {
moved.print("hello");
}

TEST(OStreamTest, MoveWhileHoldingData) {
{
fmt::ostream out = fmt::output_file("test-file");
out.print("Hello, ");
fmt::ostream moved(std::move(out));
moved.print("world!\n");
}
{
file in("test-file", file::RDONLY);
EXPECT_READ(in, "Hello, world!\n");
}
}

TEST(OStreamTest, Print) {
fmt::ostream out = fmt::output_file("test-file");
out.print("The answer is {}.\n", fmt::join(std::initializer_list<int>{42}, ", "));
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