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authorGravatar Roman Gershman <romange@gmail.com>2019-05-23 06:03:35 +0300
committerGravatar Derek Mauro <761129+derekmauro@users.noreply.github.com>2019-05-22 23:03:35 -0400
commit27c30ec671cb7b5ba84c4e79feff7fd0b0ac6338 (patch)
tree2a66b5c72434251348d3cac81314e638848043c1 /absl/strings
parentce65f5ac3cbf897bb5e3de1a51d80fd00866abaa (diff)
Avoid undefined behavior when nullptr is passed to memcpy with size 0
Diffstat (limited to 'absl/strings')
-rw-r--r--absl/strings/str_cat.cc16
-rw-r--r--absl/strings/str_cat_test.cc14
2 files changed, 25 insertions, 5 deletions
diff --git a/absl/strings/str_cat.cc b/absl/strings/str_cat.cc
index 2667976d..ffe99db8 100644
--- a/absl/strings/str_cat.cc
+++ b/absl/strings/str_cat.cc
@@ -89,7 +89,9 @@ static char* Append(char* out, const AlphaNum& x) {
// memcpy is allowed to overwrite arbitrary memory, so doing this after the
// call would force an extra fetch of x.size().
char* after = out + x.size();
- memcpy(out, x.data(), x.size());
+ if (x.size() != 0) {
+ memcpy(out, x.data(), x.size());
+ }
return after;
}
@@ -146,8 +148,10 @@ std::string CatPieces(std::initializer_list<absl::string_view> pieces) {
char* out = begin;
for (const absl::string_view piece : pieces) {
const size_t this_size = piece.size();
- memcpy(out, piece.data(), this_size);
- out += this_size;
+ if (this_size != 0) {
+ memcpy(out, piece.data(), this_size);
+ out += this_size;
+ }
}
assert(out == begin + result.size());
return result;
@@ -176,8 +180,10 @@ void AppendPieces(std::string* dest,
char* out = begin + old_size;
for (const absl::string_view piece : pieces) {
const size_t this_size = piece.size();
- memcpy(out, piece.data(), this_size);
- out += this_size;
+ if (this_size != 0) {
+ memcpy(out, piece.data(), this_size);
+ out += this_size;
+ }
}
assert(out == begin + dest->size());
}
diff --git a/absl/strings/str_cat_test.cc b/absl/strings/str_cat_test.cc
index 1f1051d4..29db9c02 100644
--- a/absl/strings/str_cat_test.cc
+++ b/absl/strings/str_cat_test.cc
@@ -408,6 +408,20 @@ TEST(StrCat, VectorBoolReferenceTypes) {
EXPECT_EQ(result, "1010");
}
+// Passing nullptr to memcpy is undefined behavior and this test
+// provides coverage of codepaths that handle empty strings with nullptrs.
+TEST(StrCat, AvoidsMemcpyWithNullptr) {
+ EXPECT_EQ(absl::StrCat(42, absl::string_view{}), "42");
+
+ // Cover CatPieces code.
+ EXPECT_EQ(absl::StrCat(1, 2, 3, 4, 5, absl::string_view{}), "12345");
+
+ // Cover AppendPieces.
+ std::string result;
+ absl::StrAppend(&result, 1, 2, 3, 4, 5, absl::string_view{});
+ EXPECT_EQ(result, "12345");
+}
+
#ifdef GTEST_HAS_DEATH_TEST
TEST(StrAppend, Death) {
std::string s = "self";