Demo style fixes and modernisation.

Address some style issues in the demos and modernise the C.
Fix the exit/return from main handling.
Reviewed-by: NAndy Polyakov <appro@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/3914)

demos/bio/saccept.c

 /*
- * Copyright 1998-2016 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 1998-2017 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the OpenSSL license (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
@@ -19,12 +19,13 @@
 
 #include <stdio.h>
 #include <signal.h>
+#include <stdlib.h>
 #include <openssl/err.h>
 #include <openssl/ssl.h>
 
 #define CERT_FILE       "server.pem"
 
-static int done = 0;
+static volatile int done = 0;
 
 void interrupt(int sig)
 {
@@ -51,7 +52,7 @@ int main(int argc, char *argv[])
     BIO *ssl_bio, *tmp;
     SSL_CTX *ctx;
     char buf[512];
-    int ret = 1, i;
+    int ret = EXIT_FAILURE, i;
 
     if (argc <= 1)
         port = "*:4433";
@@ -111,12 +112,10 @@ int main(int argc, char *argv[])
         fflush(stdout);
     }
 
-    ret = 0;
+    ret = EXIT_SUCCESS;
  err:
-    if (ret) {
+    if (ret != EXIT_SUCCESS)
         ERR_print_errors_fp(stderr);
-    }
     BIO_free(in);
-    exit(ret);
-    return (!ret);
+    return ret;
 }

demos/bio/sconnect.c

 /*
- * Copyright 1998-2016 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 1998-2017 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the OpenSSL license (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
@@ -18,17 +18,14 @@
 #include <stdlib.h>
 #include <unistd.h>
 #include <string.h>
+#include <errno.h>
 #include <openssl/err.h>
 #include <openssl/ssl.h>
 
 #define HOSTPORT "localhost:4433"
 #define CAFILE "root.pem"
 
-extern int errno;
-
-int main(argc, argv)
-int argc;
-char *argv[];
+int main(int argc, char *argv[])
 {
     const char *hostport = HOSTPORT;
     const char *CAfile = CAFILE;
@@ -39,7 +36,7 @@ char *argv[];
     SSL_CTX *ssl_ctx = NULL;
     SSL *ssl;
     BIO *ssl_bio;
-    int i, len, off, ret = 1;
+    int i, len, off, ret = EXIT_FAILURE;
 
     if (argc > 1)
         hostport = argv[1];
@@ -115,17 +112,18 @@ char *argv[];
         fwrite(buf, 1, i, stdout);
     }
 
-    ret = 1;
+    ret = EXIT_SUCCESS;
     goto done;
 
  err:
     if (ERR_peek_error() == 0) { /* system call error */
         fprintf(stderr, "errno=%d ", errno);
         perror("error");
-    } else
+    } else {
         ERR_print_errors_fp(stderr);
+    }
  done:
     BIO_free_all(out);
     SSL_CTX_free(ssl_ctx);
-    return (ret == 1);
+    return ret;
 }

demos/bio/server-arg.c

 /*
- * Copyright 2013-2016 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 2013-2017 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the OpenSSL license (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
@@ -16,6 +16,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <signal.h>
+#include <stdlib.h>
 #include <openssl/err.h>
 #include <openssl/ssl.h>
 
@@ -27,7 +28,7 @@ int main(int argc, char *argv[])
     SSL_CONF_CTX *cctx;
     char buf[512];
     BIO *in = NULL;
-    int ret = 1, i;
+    int ret = EXIT_FAILURE, i;
     char **args = argv + 1;
     int nargs = argc - 1;
 
@@ -134,12 +135,10 @@ int main(int argc, char *argv[])
         fflush(stdout);
     }
 
-    ret = 0;
+    ret = EXIT_SUCCESS;
  err:
-    if (ret) {
+    if (ret != EXIT_SUCCESS)
         ERR_print_errors_fp(stderr);
-    }
     BIO_free(in);
-    exit(ret);
-    return (!ret);
+    return ret;
 }

demos/bio/server-cmod.c

 /*
- * Copyright 2015-2016 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 2015-2017 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the OpenSSL license (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
@@ -14,6 +14,7 @@
 
 #include <stdio.h>
 #include <signal.h>
+#include <stdlib.h>
 #include <openssl/err.h>
 #include <openssl/ssl.h>
 #include <openssl/conf.h>
@@ -25,7 +26,7 @@ int main(int argc, char *argv[])
     BIO *in = NULL;
     BIO *ssl_bio, *tmp;
     SSL_CTX *ctx;
-    int ret = 1, i;
+    int ret = EXIT_FAILURE, i;
 
     ctx = SSL_CTX_new(TLS_server_method());
 
@@ -84,12 +85,10 @@ int main(int argc, char *argv[])
         fflush(stdout);
     }
 
-    ret = 0;
+    ret = EXIT_SUCCESS;
  err:
-    if (ret) {
+    if (ret != EXIT_SUCCESS)
         ERR_print_errors_fp(stderr);
-    }
     BIO_free(in);
-    exit(ret);
-    return (!ret);
+    return ret;
 }

demos/bio/server-conf.c

 /*
- * Copyright 2013-2016 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 2013-2017 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the OpenSSL license (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
@@ -16,6 +16,7 @@
 #include <stdio.h>
 #include <string.h>
 #include <signal.h>
+#include <stdlib.h>
 #include <openssl/err.h>
 #include <openssl/ssl.h>
 #include <openssl/conf.h>
@@ -32,7 +33,7 @@ int main(int argc, char *argv[])
     CONF_VALUE *cnf;
     long errline = -1;
     char buf[512];
-    int ret = 1, i;
+    int ret = EXIT_FAILURE, i;
 
     ctx = SSL_CTX_new(TLS_server_method());
 
@@ -129,12 +130,10 @@ int main(int argc, char *argv[])
         fflush(stdout);
     }
 
-    ret = 0;
+    ret = EXIT_SUCCESS;
  err:
-    if (ret) {
+    if (ret != EXIT_SUCCESS)
         ERR_print_errors_fp(stderr);
-    }
     BIO_free(in);
-    exit(ret);
-    return (!ret);
+    return ret;
 }