tidy-up: make conditional checks more consistent

... remove '== NULL' and '!= 0'

Closes #6912

docs/examples/curlx.c

@@ -372,7 +372,7 @@ int main(int argc, char **argv)
     args++;
   }
 
-  if(mimetype == NULL || mimetypeaccept == NULL || p.p12file == NULL)
+  if(!mimetype || !mimetypeaccept || !p.p12file)
     badarg = 1;
 
   if(badarg) {
@@ -385,11 +385,11 @@ int main(int argc, char **argv)
   /* set input */
 
   in = BIO_new(BIO_s_file());
-  if(in == NULL) {
+  if(!in) {
     BIO_printf(p.errorbio, "Error setting input bio\n");
     goto err;
   }
-  else if(infile == NULL)
+  else if(!infile)
     BIO_set_fp(in, stdin, BIO_NOCLOSE|BIO_FP_TEXT);
   else if(BIO_read_filename(in, infile) <= 0) {
     BIO_printf(p.errorbio, "Error opening input file %s\n", infile);
@@ -400,11 +400,11 @@ int main(int argc, char **argv)
   /* set output  */
 
   out = BIO_new(BIO_s_file());
-  if(out == NULL) {
+  if(!out) {
     BIO_printf(p.errorbio, "Error setting output bio.\n");
     goto err;
   }
-  else if(outfile == NULL)
+  else if(!outfile)
     BIO_set_fp(out, stdout, BIO_NOCLOSE|BIO_FP_TEXT);
   else if(BIO_write_filename(out, outfile) <= 0) {
     BIO_printf(p.errorbio, "Error opening output file %s\n", outfile);
@@ -453,8 +453,8 @@ int main(int argc, char **argv)
     serverurl = malloc(len);
     snprintf(serverurl, len, "https://%s", hostporturl);
   }
-  else if(p.accesstype != 0) { /* see whether we can find an AIA or SIA for a
-                                  given access type */
+  else if(p.accesstype) { /* see whether we can find an AIA or SIA for a
+                             given access type */
     serverurl = my_get_ext(p.usercert, p.accesstype, NID_info_access);
     if(!serverurl) {
       int j = 0;

docs/examples/externalsocket.c

@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -98,7 +98,7 @@ int main(void)
 #ifdef WIN32
   WSADATA wsaData;
   int initwsa = WSAStartup(MAKEWORD(2, 0), &wsaData);
-  if(initwsa != 0) {
+  if(initwsa) {
     printf("WSAStartup failed: %d\n", initwsa);
     return 1;
   }

docs/examples/fopen.c

@@ -13,7 +13,7 @@
  * See the main() function at the bottom that shows an app that retrieves from
  * a specified url using fgets() and fread() and saves as two output files.
  *
- * Copyright (c) 2003 - 2019 Simtec Electronics
+ * Copyright (c) 2003 - 2021 Simtec Electronics
  *
  * Re-implemented by Vincent Sanders <vince@kyllikki.org> with extensive
  * reference to original curl example code
@@ -107,7 +107,7 @@ static size_t write_callback(char *buffer,
   if(size > rembuff) {
     /* not enough space in buffer */
     newbuff = realloc(url->buffer, url->buffer_len + (size - rembuff));
-    if(newbuff == NULL) {
+    if(!newbuff) {
       fprintf(stderr, "callback buffer grow failed\n");
       size = rembuff;
     }

docs/examples/getinmemory.c

@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 1998 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 1998 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -43,7 +43,7 @@ WriteMemoryCallback(void *contents, size_t size, size_t nmemb, void *userp)
   struct MemoryStruct *mem = (struct MemoryStruct *)userp;
 
   char *ptr = realloc(mem->memory, mem->size + realsize + 1);
-  if(ptr == NULL) {
+  if(!ptr) {
     /* out of memory! */
     printf("not enough memory (realloc returned NULL)\n");
     return 0;

docs/examples/rtsp.c

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2011 - 2020, Jim Hollinger
+ * Copyright (c) 2011 - 2021, Jim Hollinger
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -94,7 +94,7 @@ static void rtsp_describe(CURL *curl, const char *uri,
   CURLcode res = CURLE_OK;
   FILE *sdp_fp = fopen(sdp_filename, "wb");
   printf("\nRTSP: DESCRIBE %s\n", uri);
-  if(sdp_fp == NULL) {
+  if(!sdp_fp) {
     fprintf(stderr, "Could not open '%s' for writing\n", sdp_filename);
     sdp_fp = stdout;
   }
@@ -202,10 +202,10 @@ int main(int argc, char * const argv[])
   /* check command line */
   if((argc != 2) && (argc != 3)) {
     base_name = strrchr(argv[0], '/');
-    if(base_name == NULL) {
+    if(!base_name) {
       base_name = strrchr(argv[0], '\\');
     }
-    if(base_name == NULL) {
+    if(!base_name) {
       base_name = argv[0];
     }
     else {

docs/examples/usercertinmem.c

@@ -5,7 +5,7 @@
  *                            | (__| |_| |  _ <| |___
  *                             \___|\___/|_| \_\_____|
  *
- * Copyright (C) 2013 - 2020, Daniel Stenberg, <daniel@haxx.se>, et al.
+ * Copyright (C) 2013 - 2021, Daniel Stenberg, <daniel@haxx.se>, et al.
  *
  * This software is licensed as described in the file COPYING, which
  * you should have received as part of this distribution. The terms
@@ -119,7 +119,7 @@ static CURLcode sslctx_function(CURL *curl, void *sslctx, void *parm)
   /* get a BIO */
   bio = BIO_new_mem_buf((char *)mypem, -1);
 
-  if(bio == NULL) {
+  if(!bio) {
     printf("BIO_new_mem_buf failed\n");
   }
 
@@ -127,7 +127,7 @@ static CURLcode sslctx_function(CURL *curl, void *sslctx, void *parm)
    * structure that SSL can use
    */
   cert = PEM_read_bio_X509(bio, NULL, 0, NULL);
-  if(cert == NULL) {
+  if(!cert) {
     printf("PEM_read_bio_X509 failed...\n");
   }
 
@@ -139,13 +139,13 @@ static CURLcode sslctx_function(CURL *curl, void *sslctx, void *parm)
 
   /*create a bio for the RSA key*/
   kbio = BIO_new_mem_buf((char *)mykey, -1);
-  if(kbio == NULL) {
+  if(!kbio) {
     printf("BIO_new_mem_buf failed\n");
   }
 
   /*read the key bio into an RSA object*/
   rsa = PEM_read_bio_RSAPrivateKey(kbio, NULL, 0, NULL);
-  if(rsa == NULL) {
+  if(!rsa) {
     printf("Failed to create key bio\n");
   }