LibC: Implement strerror_r()

This implements the XSI-compliant version of strerror_r() - as opposed
to the GNU-specific variant.

The function explicitly saves errno so as to not accidentally change it
with one of the calls to other functions.

2 files changed, 19 insertions, 0 deletions

diff --git a/Tests/LibC/CMakeLists.txt b/Tests/LibC/CMakeLists.txt
index d18144aff4..a4f8a4ce0b 100644
--- a/Tests/LibC/CMakeLists.txt
+++ b/Tests/LibC/CMakeLists.txt
@@ -6,6 +6,7 @@ set(TEST_SOURCES
     ${CMAKE_CURRENT_SOURCE_DIR}/TestLibCExec.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/TestLibCDirEnt.cpp
     ${CMAKE_CURRENT_SOURCE_DIR}/TestLibCInodeWatcher.cpp
+    ${CMAKE_CURRENT_SOURCE_DIR}/TestLibCString.cpp
 )
 
 file(GLOB CMD_SOURCES  CONFIGURE_DEPENDS "*.cpp")
diff --git a/Tests/LibC/TestLibCString.cpp b/Tests/LibC/TestLibCString.cpp
new file mode 100644
index 0000000000..57ff705657
--- /dev/null
+++ b/Tests/LibC/TestLibCString.cpp
@@ -0,0 +1,18 @@
+/*
+ * Copyright (c) 2021, Gunnar Beutner <gbeutner@serenityos.org>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <LibTest/TestCase.h>
+#include <errno.h>
+#include <string.h>
+
+TEST_CASE(strerror_r_basic)
+{
+    EXPECT_EQ(strerror_r(1000, nullptr, 0), EINVAL);
+    EXPECT_EQ(strerror_r(EFAULT, nullptr, 0), ERANGE);
+    char buf[64];
+    EXPECT_EQ(strerror_r(EFAULT, buf, sizeof(buf)), 0);
+    EXPECT_EQ(strcmp(buf, "Bad address"), 0);
+}