diff --git a/src/getopt.c b/src/getopt.c
index a59a013..98a6f33 100644
--- a/src/getopt.c
+++ b/src/getopt.c
@@ -52,6 +52,7 @@ char *alloca ();
 #endif
 
 #include <stdio.h>
+#include <string.h>
 
 /* Comment out all this code if we are using the GNU C Library, and are not
    actually compiling the library itself.  This code is part of the GNU C
diff --git a/src/md5.c b/src/md5.c
index d6b8013..e20c053 100644
--- a/src/md5.c
+++ b/src/md5.c
@@ -24,19 +24,12 @@
 # include <config.h>
 #endif
 
-#include <sys/types.h>
-
-#if STDC_HEADERS || defined _LIBC
-# include <stdlib.h>
-# include <string.h>
-#else
-# ifndef HAVE_MEMCPY
-#  define memcpy(d, s, n) bcopy ((s), (d), (n))
-# endif
-#endif
-
 #include "md5.h"
 
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+
 #ifdef _LIBC
 # include <endian.h>
 # if __BYTE_ORDER == __BIG_ENDIAN
@@ -69,8 +62,7 @@ static const unsigned char fillbuf[64] = { 0x80, 0 /* , 0, 0, ...  */ };
 /* Initialize structure containing state of computation.
    (RFC 1321, 3.3: Step 3)  */
 void
-md5_init_ctx (ctx)
-     struct md5_ctx *ctx;
+md5_init_ctx (struct md5_ctx *ctx)
 {
   ctx->A = 0x67452301;
   ctx->B = 0xefcdab89;
@@ -87,9 +79,7 @@ md5_init_ctx (ctx)
    IMPORTANT: On some systems it is required that RESBUF is correctly
    aligned for a 32 bits value.  */
 void *
-md5_read_ctx (ctx, resbuf)
-     const struct md5_ctx *ctx;
-     void *resbuf;
+md5_read_ctx (const struct md5_ctx *ctx, void *resbuf)
 {
   ((md5_uint32 *) resbuf)[0] = SWAP (ctx->A);
   ((md5_uint32 *) resbuf)[1] = SWAP (ctx->B);
@@ -105,9 +95,7 @@ md5_read_ctx (ctx, resbuf)
    IMPORTANT: On some systems it is required that RESBUF is correctly
    aligned for a 32 bits value.  */
 void *
-md5_finish_ctx (ctx, resbuf)
-     struct md5_ctx *ctx;
-     void *resbuf;
+md5_finish_ctx (struct md5_ctx *ctx, void *resbuf)
 {
   /* Take yet unprocessed bytes into account.  */
   md5_uint32 bytes = ctx->buflen;
@@ -136,9 +124,7 @@ md5_finish_ctx (ctx, resbuf)
    resulting message digest number will be written into the 16 bytes
    beginning at RESBLOCK.  */
 int
-md5_stream (stream, resblock)
-     FILE *stream;
-     void *resblock;
+md5_stream (FILE *stream, void *resblock)
 {
   /* Important: BLOCKSIZE must be a multiple of 64.  */
 #define BLOCKSIZE 4096
@@ -193,10 +179,7 @@ md5_stream (stream, resblock)
    output yields to the wanted ASCII representation of the message
    digest.  */
 void *
-md5_buffer (buffer, len, resblock)
-     const char *buffer;
-     size_t len;
-     void *resblock;
+md5_buffer (const char *buffer, size_t len, void *resblock)
 {
   struct md5_ctx ctx;
 
@@ -212,10 +195,7 @@ md5_buffer (buffer, len, resblock)
 
 
 void
-md5_process_bytes (buffer, len, ctx)
-     const void *buffer;
-     size_t len;
-     struct md5_ctx *ctx;
+md5_process_bytes (const void *buffer, size_t len, struct md5_ctx *ctx)
 {
   //const void aligned_buffer = buffer;
 
@@ -285,10 +265,7 @@ md5_process_bytes (buffer, len, ctx)
    It is assumed that LEN % 64 == 0.  */
 
 void
-md5_process_block (buffer, len, ctx)
-     const void *buffer;
-     size_t len;
-     struct md5_ctx *ctx;
+md5_process_block (const void *buffer, size_t len, struct md5_ctx *ctx)
 {
   md5_uint32 correct_words[16];
   const md5_uint32 *words = buffer;
diff --git a/src/md5.h b/src/md5.h
index 6febd4a..3ff0378 100644
--- a/src/md5.h
+++ b/src/md5.h
@@ -22,10 +22,7 @@
 #define _MD5_H 1
 
 #include <stdio.h>
-
-#if defined HAVE_LIMITS_H || _LIBC
-# include <limits.h>
-#endif
+#include <limits.h>
 
 /* The following contortions are an attempt to use the C preprocessor
    to determine an unsigned integral type that is 32 bits wide.  An
@@ -38,20 +35,7 @@
 # include <sys/types.h>
 typedef u_int32_t md5_uint32;
 #else
-# if defined __STDC__ && __STDC__
-#  define UINT_MAX_32_BITS 4294967295U
-# else
-#  define UINT_MAX_32_BITS 0xFFFFFFFF
-# endif
-
-/* If UINT_MAX isn't defined, assume it's a 32-bit type.
-   This should be valid for all systems GNU cares about because
-   that doesn't include 16-bit systems, and only modern systems
-   (that certainly have <limits.h>) have 64+-bit integral types.  */
-
-# ifndef UINT_MAX
-#  define UINT_MAX UINT_MAX_32_BITS
-# endif
+#define UINT_MAX_32_BITS 4294967295U
 
 # if UINT_MAX == UINT_MAX_32_BITS
    typedef unsigned int md5_uint32;