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Fix an overflow in format_to_n (#2029)

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This commit is contained in:
Victor Zverovich 2020-11-18 06:43:47 -08:00
parent 6cdd1be93e
commit 2c734c9bca
2 changed files with 6 additions and 1 deletions
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2
include/fmt/core.h
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@ -766,7 +766,7 @@ class fixed_buffer_traits {
explicit fixed_buffer_traits(size_t limit) : limit_(limit) {} explicit fixed_buffer_traits(size_t limit) : limit_(limit) {}
size_t count() const { return count_; } size_t count() const { return count_; }
size_t limit(size_t size) { size_t limit(size_t size) {
size_t n = limit_ - count_; size_t n = limit_ > count_ ? limit_ - count_ : 0;
count_ += size; count_ += size;
return size < n ? size : n; return size < n ? size : n;
} }

5
test/format-test.cc
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@ -2031,6 +2031,11 @@ TEST(FormatTest, FormatToN) {
result = fmt::format_to_n(buffer, 4, "{}", "ABCDE"); result = fmt::format_to_n(buffer, 4, "{}", "ABCDE");
EXPECT_EQ(5u, result.size); EXPECT_EQ(5u, result.size);
EXPECT_EQ("ABCD", fmt::string_view(buffer, 4)); EXPECT_EQ("ABCD", fmt::string_view(buffer, 4));
buffer[3] = 'x';
result = fmt::format_to_n(buffer, 3, "{}", std::string(1000, '*'));
EXPECT_EQ(1000u, result.size);
EXPECT_EQ("***x", fmt::string_view(buffer, 4));
} }
TEST(FormatTest, WideFormatToN) { TEST(FormatTest, WideFormatToN) {