diff --git a/reactos/lib/sdk/crt/math/abs.c b/reactos/lib/sdk/crt/math/abs.c
index 24f6351b574..a95798b8de4 100644
--- a/reactos/lib/sdk/crt/math/abs.c
+++ b/reactos/lib/sdk/crt/math/abs.c
@@ -4,8 +4,10 @@
 /*
  * @implemented
  */
+#ifndef _MSC_VER
 int
 abs(int j)
 {
   return j<0 ? -j : j;
 }
+#endif
diff --git a/reactos/lib/sdk/crt/math/labs.c b/reactos/lib/sdk/crt/math/labs.c
index 680f3ee0335..e19c211c99b 100644
--- a/reactos/lib/sdk/crt/math/labs.c
+++ b/reactos/lib/sdk/crt/math/labs.c
@@ -4,8 +4,10 @@
 /*
  * @implemented
  */
+#ifndef _MSC_VER
 long
 labs(long j)
 {
   return j<0 ? -j : j;
 }
+#endif
diff --git a/reactos/lib/sdk/crt/string/ctype.c b/reactos/lib/sdk/crt/string/ctype.c
index 5c5f4549b33..99bec2b6968 100644
--- a/reactos/lib/sdk/crt/string/ctype.c
+++ b/reactos/lib/sdk/crt/string/ctype.c
@@ -3,6 +3,24 @@
 
 #undef _pctype
 
+/* MS's CRT header defines all that, and we actually implement that */
+#undef iswalnum
+#undef __isascii
+#undef iswascii
+#undef __iscsym
+#undef __iscsymf
+#undef iswalpha
+#undef iswcntrl
+#undef iswdigit
+#undef iswgraph
+#undef iswprint
+#undef iswpunct
+#undef iswlower
+#undef iswupper
+#undef iswspace
+#undef iswxdigit
+#undef __toascii
+
 #define upalpha ('A' - 'a')
 
 
diff --git a/reactos/lib/sdk/crt/string/sscanf.c b/reactos/lib/sdk/crt/string/sscanf.c
index bd3b446dc6d..80f65d9fd1c 100644
--- a/reactos/lib/sdk/crt/string/sscanf.c
+++ b/reactos/lib/sdk/crt/string/sscanf.c
@@ -6,6 +6,9 @@
 #define NDEBUG
 #include <internal/debug.h>
 
+#ifndef TRACE
+#define TRACE DPRINT
+#endif
 #define WARN DPRINT1
 
 
@@ -26,6 +29,11 @@ static int char2digit(char c, int base) {
 #undef WIDE_SCANF
 #undef CONSOLE
 #define STRING 1
+
+#ifdef _MSC_VER
+#define debugstr_a(x) x
+#endif
+
 #include "wine/scanf.h"
 
 int sscanf(const char *str, const char *format, ...)
diff --git a/reactos/lib/sdk/crt/string/strset.c b/reactos/lib/sdk/crt/string/strset.c
index ee4fd708595..db44dd26f8d 100644
--- a/reactos/lib/sdk/crt/string/strset.c
+++ b/reactos/lib/sdk/crt/string/strset.c
@@ -30,6 +30,7 @@ char* _strnset(char* szToFill, int szFill, size_t sizeMaxFill)
 /*
  * @implemented
  */
+#ifndef _MSC_VER
 char* _strset(char* szToFill, int szFill)
 {
 	char *t = szToFill;
@@ -41,3 +42,4 @@ char* _strset(char* szToFill, int szFill)
 	}
 	return t;
 }
+#endif
diff --git a/reactos/lib/sdk/crt/wstring/wcsset.c b/reactos/lib/sdk/crt/wstring/wcsset.c
index 59932e06a23..a4a5a504399 100644
--- a/reactos/lib/sdk/crt/wstring/wcsset.c
+++ b/reactos/lib/sdk/crt/wstring/wcsset.c
@@ -30,6 +30,7 @@ wchar_t* _wcsnset (wchar_t* wsToFill, wchar_t wcFill, size_t sizeMaxFill)
 /*
  * @implemented
  */
+#ifndef _MSC_VER
 wchar_t* _wcsset (wchar_t* wsToFill, wchar_t wcFill)
 {
 	wchar_t *t = wsToFill;
@@ -41,3 +42,4 @@ wchar_t* _wcsset (wchar_t* wsToFill, wchar_t wcFill)
 	}
 	return t;
 }
+#endif