[compiler-rt] Add internal implementations for strlcat and strlcpy

The compiler-rt should make use of strlcpy() rather than strncpy(). Using internal_strncpy() may be fine with appropriate bounds checking or enforcement of nul-termination elsewhere, but it's just good practice these days to avoid using strncpy() in new code.

A patch by Jeremy Sequoia!

Differential Revision: http://reviews.llvm.org/D14714

llvm-svn: 253690

compiler-rt/lib/sanitizer_common/sanitizer_libc.cc

@@ -175,6 +175,19 @@ uptr internal_strlen(const char *s) {
   return i;
 }
 
+uptr internal_strlcat(char *dst, const char *src, uptr maxlen) {
+  const uptr srclen = internal_strlen(src);
+  const uptr dstlen = internal_strnlen(dst, maxlen);
+  if (dstlen == maxlen) return maxlen + srclen;
+  if (srclen < maxlen - dstlen) {
+    internal_memmove(dst + dstlen, src, srclen + 1);
+  } else {
+    internal_memmove(dst + dstlen, src, maxlen - dstlen - 1);
+    dst[maxlen - 1] = '\0';
+  }
+  return dstlen + srclen;
+}
+
 char *internal_strncat(char *dst, const char *src, uptr n) {
   uptr len = internal_strlen(dst);
   uptr i;
@@ -184,6 +197,17 @@ char *internal_strncat(char *dst, const char *src, uptr n) {
   return dst;
 }
 
+uptr internal_strlcpy(char *dst, const char *src, uptr maxlen) {
+  const uptr srclen = internal_strlen(src);
+  if (srclen < maxlen) {
+    internal_memmove(dst, src, srclen + 1);
+  } else if (maxlen != 0) {
+    internal_memmove(dst, src, maxlen - 1);
+    dst[maxlen - 1] = '\0';
+  }
+  return srclen;
+}
+
 char *internal_strncpy(char *dst, const char *src, uptr n) {
   uptr i;
   for (i = 0; i < n && src[i]; i++)

compiler-rt/lib/sanitizer_common/sanitizer_libc.h

@@ -43,8 +43,10 @@ uptr internal_strcspn(const char *s, const char *reject);
 char *internal_strdup(const char *s);
 char *internal_strndup(const char *s, uptr n);
 uptr internal_strlen(const char *s);
+uptr internal_strlcat(char *dst, const char *src, uptr maxlen);
 char *internal_strncat(char *dst, const char *src, uptr n);
 int internal_strncmp(const char *s1, const char *s2, uptr n);
+uptr internal_strlcpy(char *dst, const char *src, uptr maxlen);
 char *internal_strncpy(char *dst, const char *src, uptr n);
 uptr internal_strnlen(const char *s, uptr maxlen);
 char *internal_strrchr(const char *s, int c);

compiler-rt/lib/sanitizer_common/tests/sanitizer_libc_test.cc

@@ -8,6 +8,7 @@
 //===----------------------------------------------------------------------===//
 // Tests for sanitizer_libc.h.
 //===----------------------------------------------------------------------===//
+#include <algorithm>
 
 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_libc.h"
@@ -145,12 +146,65 @@ TEST(SanitizerCommon, FileOps) {
 #endif
 }
 
+static const size_t kStrlcpyBufSize = 8;
+void test_internal_strlcpy(char *dbuf, const char *sbuf) {
+  uptr retval = 0;
+  retval = internal_strlcpy(dbuf, sbuf, kStrlcpyBufSize);
+  EXPECT_EQ(internal_strncmp(dbuf, sbuf, kStrlcpyBufSize - 1), 0);
+  EXPECT_EQ(internal_strlen(dbuf),
+            std::min(internal_strlen(sbuf), (uptr)(kStrlcpyBufSize - 1)));
+  EXPECT_EQ(retval, internal_strlen(sbuf));
+
+  // Test with shorter maxlen.
+  uptr maxlen = 2;
+  if (internal_strlen(sbuf) > maxlen) {
+    retval = internal_strlcpy(dbuf, sbuf, maxlen);
+    EXPECT_EQ(internal_strncmp(dbuf, sbuf, maxlen - 1), 0);
+    EXPECT_EQ(internal_strlen(dbuf), maxlen - 1);
+  }
+}
+
 TEST(SanitizerCommon, InternalStrFunctions) {
   const char *haystack = "haystack";
   EXPECT_EQ(haystack + 2, internal_strchr(haystack, 'y'));
   EXPECT_EQ(haystack + 2, internal_strchrnul(haystack, 'y'));
   EXPECT_EQ(0, internal_strchr(haystack, 'z'));
   EXPECT_EQ(haystack + 8, internal_strchrnul(haystack, 'z'));
+
+  char dbuf[kStrlcpyBufSize] = {};
+  const char *samesizestr = "1234567";
+  const char *shortstr = "123";
+  const char *longerstr = "123456789";
+
+  // Test internal_strlcpy.
+  internal_strlcpy(dbuf, shortstr, 0);
+  EXPECT_EQ(dbuf[0], 0);
+  EXPECT_EQ(dbuf[0], 0);
+  test_internal_strlcpy(dbuf, samesizestr);
+  test_internal_strlcpy(dbuf, shortstr);
+  test_internal_strlcpy(dbuf, longerstr);
+
+  // Test internal_strlcat.
+  char dcatbuf[kStrlcpyBufSize] = {};
+  uptr retval = 0;
+  retval = internal_strlcat(dcatbuf, "aaa", 0);
+  EXPECT_EQ(internal_strlen(dcatbuf), (uptr)0);
+  EXPECT_EQ(retval, (uptr)3);
+
+  retval = internal_strlcat(dcatbuf, "123", kStrlcpyBufSize);
+  EXPECT_EQ(internal_strcmp(dcatbuf, "123"), 0);
+  EXPECT_EQ(internal_strlen(dcatbuf), (uptr)3);
+  EXPECT_EQ(retval, (uptr)3);
+
+  retval = internal_strlcat(dcatbuf, "123", kStrlcpyBufSize);
+  EXPECT_EQ(internal_strcmp(dcatbuf, "123123"), 0);
+  EXPECT_EQ(internal_strlen(dcatbuf), (uptr)6);
+  EXPECT_EQ(retval, (uptr)6);
+
+  retval = internal_strlcat(dcatbuf, "123", kStrlcpyBufSize);
+  EXPECT_EQ(internal_strcmp(dcatbuf, "1231231"), 0);
+  EXPECT_EQ(internal_strlen(dcatbuf), (uptr)7);
+  EXPECT_EQ(retval, (uptr)9);
 }
 
 // FIXME: File manipulations are not yet supported on Windows