diff --git a/src/gmio_core/internal/string_utils.h b/src/gmio_core/internal/string_utils.h
index 81215d7..a43b92c 100644
--- a/src/gmio_core/internal/string_utils.h
+++ b/src/gmio_core/internal/string_utils.h
@@ -18,14 +18,57 @@
 
 #include "../global.h"
 
+/*! Returns non-zero if \p c is a space (for C-locale), zero otherwise */
+GMIO_INLINE int gmio_clocale_isspace(char c);
+
+/*! Returns non-zero if \p c is a digit (for C-locale), zero otherwise */
+GMIO_INLINE int gmio_clocale_isdigit(char c);
+
+/*! Returns non-zero if \p c is an uppercase letter (for C-locale), zero
+ *  otherwise */
+GMIO_INLINE int gmio_clocale_isupper(char c);
+
+/*! Returns non-zero if \p c is a lowercase letter (for C-locale), zero
+ *  otherwise */
+GMIO_INLINE int gmio_clocale_islower(char c);
+
+/*! Returns the lowercase letter converted to uppercase */
+GMIO_INLINE char gmio_clocale_toupper(char c);
+
+/*! Returns the uppercase letter converted to lowercase */
+GMIO_INLINE char gmio_clocale_tolower(char c);
+
+/*! Returns true if \p c1 compare equals to \p c2
+ *
+ *  Comparison is case-insensitive
+ */
+GMIO_INLINE gmio_bool_t gmio_clocale_char_iequals(char c1, char c2);
+
+/*! Returns 0 if \p str1 and \p str2 compare equal, non-zero otherwise
+ *
+ *  Comparison is case-insensitive
+ */
+GMIO_INLINE int gmio_stricmp(const char* str1, const char* str2);
+
+/*! Returns true if \p str starts with string \p begin
+ *
+ *  Comparison is case-insensitive
+ */
+GMIO_INLINE gmio_bool_t gmio_istarts_with(const char* str, const char* begin);
+
+
+
+/*
+ * -- Implementation
+ */
+
 #include <string.h>
 
 #ifdef GMIO_STRINGUTILS_CTYPE_H
 #  include <ctype.h>
 #endif
 
-/*! Returns non-zero if \p c is a space (for C-locale), zero otherwise */
-GMIO_INLINE int gmio_clocale_isspace(char c)
+int gmio_clocale_isspace(char c)
 {
     /* 0x20 : space (SPC)
      * 0x09 : horizontal tab (TAB)
@@ -61,7 +104,7 @@ GMIO_INLINE int gmio_clocale_isspace(char c)
 #endif
 }
 
-GMIO_INLINE int gmio_clocale_isdigit(char c)
+int gmio_clocale_isdigit(char c)
 {
     static const unsigned char digit_chars[] = {
         0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
@@ -84,9 +127,7 @@ GMIO_INLINE int gmio_clocale_isdigit(char c)
     return digit_chars[(unsigned char)c];
 }
 
-/*! Returns non-zero if \p c is an uppercase letter (for C-locale), zero
- *  otherwise */
-GMIO_INLINE int gmio_clocale_isupper(char c)
+int gmio_clocale_isupper(char c)
 {
 #if defined(GMIO_STRINGUTILS_DIRECT_TESTS)
     /* TODO: eliminate branch */
@@ -116,9 +157,7 @@ GMIO_INLINE int gmio_clocale_isupper(char c)
 #endif
 }
 
-/*! Returns non-zero if \p c is a lowercase letter (for C-locale), zero
- *  otherwise */
-GMIO_INLINE int gmio_clocale_islower(char c)
+int gmio_clocale_islower(char c)
 {
 #if defined(GMIO_STRINGUTILS_DIRECT_TESTS)
     /* TODO: eliminate branch */
@@ -148,8 +187,7 @@ GMIO_INLINE int gmio_clocale_islower(char c)
 #endif
 }
 
-/*! Returns the lowercase letter converted to uppercase */
-GMIO_INLINE char gmio_clocale_toupper(char c)
+char gmio_clocale_toupper(char c)
 {
     static const char table_toupper[128] = {
         0 ,  0 ,  0 ,  0 ,  0 ,  0 ,  0 ,  0 ,  0 ,0x09,0x0A,  0 ,  0 ,0x0D,  0 ,  0 ,
@@ -164,8 +202,7 @@ GMIO_INLINE char gmio_clocale_toupper(char c)
     return table_toupper[(unsigned char)c];
 }
 
-/*! Returns the uppercase letter converted to lowercase */
-GMIO_INLINE char gmio_clocale_tolower(char c)
+char gmio_clocale_tolower(char c)
 {
     static const char table_tolower[128] = {
         0 ,  0 ,  0 ,  0 ,  0 ,  0 ,  0 ,  0 ,  0 ,0x09,0x0A,  0 ,  0 ,0x0D,  0 ,  0 ,
@@ -180,21 +217,13 @@ GMIO_INLINE char gmio_clocale_tolower(char c)
     return table_tolower[(unsigned char)c];
 }
 
-/*! Returns true if \p c1 compare equals to \p c2
- *
- *  Comparison is case-insensitive
- */
-GMIO_INLINE gmio_bool_t gmio_clocale_char_iequals(char c1, char c2)
+gmio_bool_t gmio_clocale_char_iequals(char c1, char c2)
 {
     /* TODO: eliminate branch */
     return c1 == c2 || (gmio_clocale_toupper(c1) == gmio_clocale_toupper(c2));
 }
 
-/*! Returns 0 if \p str1 and \p str2 compare equal, non-zero otherwise
- *
- *  Comparison is case-insensitive
- */
-GMIO_INLINE int gmio_stricmp(const char* str1, const char* str2)
+int gmio_stricmp(const char* str1, const char* str2)
 {
     while (*str1 != 0 && *str2 != 0) {
         if (!gmio_clocale_char_iequals(*str1, *str2))
@@ -205,18 +234,11 @@ GMIO_INLINE int gmio_stricmp(const char* str1, const char* str2)
     return *str1 == 0 && *str2 == 0 ? 0 : 1;
 }
 
-/*! Returns true if \p str starts with string \p begin
- *
- *  Comparison is case-insensitive
- */
-GMIO_INLINE gmio_bool_t gmio_istarts_with(const char* str, const char* begin)
+gmio_bool_t gmio_istarts_with(const char* str, const char* begin)
 {
     while (*begin != 0) {
-        if (*str == 0
-                || gmio_clocale_char_iequals(*str, *begin) == GMIO_FALSE)
-        {
+        if (*str == 0 || !gmio_clocale_char_iequals(*str, *begin))
             return GMIO_FALSE;
-        }
         ++str;
         ++begin;
     }