[libc] Add strncat and fix strcat
This adds strncat to llvm libc. In addition, an error was found with
strcat and that was fixed.
Reviewed By: lntue
Differential Revision: https://reviews.llvm.org/D111583
GitOrigin-RevId: 9e9803bf82500b8a075d9658d2b4c248115f4a6f
diff --git a/config/linux/x86_64/entrypoints.txt b/config/linux/x86_64/entrypoints.txt
index b261a1a..56ae31d 100644
--- a/config/linux/x86_64/entrypoints.txt
+++ b/config/linux/x86_64/entrypoints.txt
@@ -35,6 +35,7 @@
libc.src.string.strcpy
libc.src.string.strcspn
libc.src.string.strlen
+ libc.src.string.strncat
libc.src.string.strncmp
libc.src.string.strncpy
libc.src.string.strnlen
diff --git a/src/string/CMakeLists.txt b/src/string/CMakeLists.txt
index aa22fa0..e5d6ebc 100644
--- a/src/string/CMakeLists.txt
+++ b/src/string/CMakeLists.txt
@@ -96,6 +96,17 @@
)
add_entrypoint_object(
+ strncat
+ SRCS
+ strncat.cpp
+ HDRS
+ strncat.h
+ DEPENDS
+ .strncpy
+ .string_utils
+)
+
+add_entrypoint_object(
strncmp
SRCS
strncmp.cpp
diff --git a/src/string/strcat.cpp b/src/string/strcat.cpp
index 176a42a..fef2758 100644
--- a/src/string/strcat.cpp
+++ b/src/string/strcat.cpp
@@ -16,7 +16,10 @@
LLVM_LIBC_FUNCTION(char *, strcat,
(char *__restrict dest, const char *__restrict src)) {
- __llvm_libc::strcpy(dest + internal::string_length(dest), src);
+ size_t destLength = internal::string_length(dest);
+ size_t srcLength = internal::string_length(src);
+ __llvm_libc::strcpy(dest + destLength, src);
+ dest[destLength + srcLength] = '\0';
return dest;
}
diff --git a/src/string/strncat.cpp b/src/string/strncat.cpp
new file mode 100644
index 0000000..968c1e2
--- /dev/null
+++ b/src/string/strncat.cpp
@@ -0,0 +1,28 @@
+//===-- Implementation of strncat -----------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/string/strncat.h"
+#include "src/string/string_utils.h"
+#include "src/string/strncpy.h"
+
+#include "src/__support/common.h"
+
+namespace __llvm_libc {
+
+LLVM_LIBC_FUNCTION(char *, strncat,
+ (char *__restrict dest, const char *__restrict src,
+ size_t count)) {
+ size_t srcLength = internal::string_length(src);
+ size_t copyAmount = srcLength > count ? count : srcLength;
+ size_t destLength = internal::string_length(dest);
+ __llvm_libc::strncpy(dest + destLength, src, copyAmount);
+ dest[destLength + copyAmount] = '\0';
+ return dest;
+}
+
+} // namespace __llvm_libc
diff --git a/src/string/strncat.h b/src/string/strncat.h
new file mode 100644
index 0000000..9b2c70f
--- /dev/null
+++ b/src/string/strncat.h
@@ -0,0 +1,20 @@
+//===-- Implementation header for strncat -----------------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_LIBC_SRC_STRING_STRNCAT_H
+#define LLVM_LIBC_SRC_STRING_STRNCAT_H
+
+#include <string.h>
+
+namespace __llvm_libc {
+
+char *strncat(char *__restrict dest, const char *__restrict src, size_t count);
+
+} // namespace __llvm_libc
+
+#endif // LLVM_LIBC_SRC_STRING_STRNCAT_H
diff --git a/test/src/string/CMakeLists.txt b/test/src/string/CMakeLists.txt
index d68c1c9..2d6d919 100644
--- a/test/src/string/CMakeLists.txt
+++ b/test/src/string/CMakeLists.txt
@@ -83,6 +83,16 @@
)
add_libc_unittest(
+ strncat_test
+ SUITE
+ libc_string_unittests
+ SRCS
+ strncat_test.cpp
+ DEPENDS
+ libc.src.string.strncat
+)
+
+add_libc_unittest(
strncmp_test
SUITE
libc_string_unittests
diff --git a/test/src/string/strncat_test.cpp b/test/src/string/strncat_test.cpp
new file mode 100644
index 0000000..f7442dc
--- /dev/null
+++ b/test/src/string/strncat_test.cpp
@@ -0,0 +1,76 @@
+//===-- Unittests for strncat ---------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "src/string/strncat.h"
+#include "utils/UnitTest/Test.h"
+
+TEST(LlvmLibcStrNCatTest, EmptyDest) {
+ const char *abc = "abc";
+ char dest[4];
+
+ dest[0] = '\0';
+
+ // Start by copying nothing
+ char *result = __llvm_libc::strncat(dest, abc, 0);
+ ASSERT_EQ(dest, result);
+ ASSERT_EQ(dest[0], '\0');
+
+ // Then copy part of it.
+ result = __llvm_libc::strncat(dest, abc, 1);
+ ASSERT_EQ(dest, result);
+ ASSERT_STREQ(dest, "a");
+
+ // Reset for the last test.
+ dest[0] = '\0';
+
+ // Then copy all of it.
+ result = __llvm_libc::strncat(dest, abc, 3);
+ ASSERT_EQ(dest, result);
+ ASSERT_STREQ(dest, result);
+ ASSERT_STREQ(dest, abc);
+}
+
+TEST(LlvmLibcStrNCatTest, NonEmptyDest) {
+ const char *abc = "abc";
+ char dest[7];
+
+ dest[0] = 'x';
+ dest[1] = 'y';
+ dest[2] = 'z';
+ dest[3] = '\0';
+
+ // Copy only part of the string onto the end
+ char *result = __llvm_libc::strncat(dest, abc, 1);
+ ASSERT_EQ(dest, result);
+ ASSERT_STREQ(dest, "xyza");
+
+ // Copy a bit more, but without resetting.
+ result = __llvm_libc::strncat(dest, abc, 2);
+ ASSERT_EQ(dest, result);
+ ASSERT_STREQ(dest, "xyzaab");
+
+ // Set just the end marker, to make sure it overwrites properly.
+ dest[3] = '\0';
+
+ result = __llvm_libc::strncat(dest, abc, 3);
+ ASSERT_EQ(dest, result);
+ ASSERT_STREQ(dest, "xyzabc");
+
+ // Check that copying still works when count > src length
+ dest[0] = '\0';
+ // And that it doesn't write beyond what is necessary.
+ dest[4] = 'Z';
+ result = __llvm_libc::strncat(dest, abc, 4);
+ ASSERT_EQ(dest, result);
+ ASSERT_STREQ(dest, "abc");
+ ASSERT_EQ(dest[4], 'Z');
+
+ result = __llvm_libc::strncat(dest, abc, 5);
+ ASSERT_EQ(dest, result);
+ ASSERT_STREQ(dest, "abcabc");
+}
