build: tidy up deprecation suppression, enable warnings for clang

Suppress deprecation warnings the closest to the deprecated code, using
`CURL_IGNORE_DEPRECATION()`. Then drop build-specific suppressions, and
file-wide ones. The latter is not compatible with Unity mode. Also
replace manual suppressions with a macro to apply to all compilers with
deprecation warning support. Also enable deprecation warnings for clang.

- curl/curl.h: enable deprecation warnings for clang.

- docs/examples: stop setting `CURL_DISABLE_DEPRECATION` with autotools.
  Suppression moved to C-level earlier. Syncs with cmake.
  Follow-up to 5fc61a37c1 #14123

- tests/http/clients: stop setting `CURL_DISABLE_DEPRECATION` in
  autotools. If it becomes necessary in the future, it can be done in
  C via the macro. Syncs with cmake.

- lib1545: stop setting `CURL_DISABLE_DEPRECATION` in autotools.
  Drop guard from test source.
  Follow-up to 0f10360073 #12444

- libtest, unit: replace `CURL_DISABLE_DEPRECATION` with
  `CURL_IGNORE_DEPRECATION()`.

- docs/examples: replace pragmas with `CURL_IGNORE_DEPRECATION()`.

Closes #14789

docs/examples/Makefile.am

@@ -34,8 +34,7 @@ EXTRA_DIST = README.md Makefile.example Makefile.mk CMakeLists.txt \
 #
 # $(top_srcdir)/include is for libcurl's external include files
 
-AM_CPPFLAGS = -I$(top_srcdir)/include   \
-              -DCURL_DISABLE_DEPRECATION
+AM_CPPFLAGS = -I$(top_srcdir)/include
 
 LIBDIR = $(top_builddir)/lib
 

docs/examples/multi-formadd.c

@@ -36,11 +36,6 @@
 
 #include <curl/curl.h>
 
-#ifdef __GNUC__
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
-#endif
-
 int main(void)
 {
   CURL *curl;
@@ -53,27 +48,29 @@ int main(void)
   struct curl_slist *headerlist = NULL;
   static const char buf[] = "Expect:";
 
-  /* Fill in the file upload field. This makes libcurl load data from
-     the given file name when curl_easy_perform() is called. */
-  curl_formadd(&formpost,
-               &lastptr,
-               CURLFORM_COPYNAME, "sendfile",
-               CURLFORM_FILE, "multi-formadd.c",
-               CURLFORM_END);
+  CURL_IGNORE_DEPRECATION(
+    /* Fill in the file upload field. This makes libcurl load data from
+       the given file name when curl_easy_perform() is called. */
+    curl_formadd(&formpost,
+                 &lastptr,
+                 CURLFORM_COPYNAME, "sendfile",
+                 CURLFORM_FILE, "multi-formadd.c",
+                 CURLFORM_END);
 
-  /* Fill in the filename field */
-  curl_formadd(&formpost,
-               &lastptr,
-               CURLFORM_COPYNAME, "filename",
-               CURLFORM_COPYCONTENTS, "multi-formadd.c",
-               CURLFORM_END);
+    /* Fill in the filename field */
+    curl_formadd(&formpost,
+                 &lastptr,
+                 CURLFORM_COPYNAME, "filename",
+                 CURLFORM_COPYCONTENTS, "multi-formadd.c",
+                 CURLFORM_END);
 
-  /* Fill in the submit field too, even if this is rarely needed */
-  curl_formadd(&formpost,
-               &lastptr,
-               CURLFORM_COPYNAME, "submit",
-               CURLFORM_COPYCONTENTS, "send",
-               CURLFORM_END);
+    /* Fill in the submit field too, even if this is rarely needed */
+    curl_formadd(&formpost,
+                 &lastptr,
+                 CURLFORM_COPYNAME, "submit",
+                 CURLFORM_COPYCONTENTS, "send",
+                 CURLFORM_END);
+  )
 
   curl = curl_easy_init();
   multi_handle = curl_multi_init();
@@ -88,7 +85,9 @@ int main(void)
     curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);
 
     curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist);
-    curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost);
+    CURL_IGNORE_DEPRECATION(
+      curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost);
+    )
 
     curl_multi_add_handle(multi_handle, curl);
 
@@ -109,15 +108,13 @@ int main(void)
     /* always cleanup */
     curl_easy_cleanup(curl);
 
-    /* then cleanup the formpost chain */
-    curl_formfree(formpost);
+    CURL_IGNORE_DEPRECATION(
+      /* then cleanup the formpost chain */
+      curl_formfree(formpost);
+    )
 
     /* free slist */
     curl_slist_free_all(headerlist);
   }
   return 0;
 }
-
-#ifdef __GNUC__
-#pragma GCC diagnostic pop
-#endif

docs/examples/postit2-formadd.c

@@ -47,11 +47,6 @@
 
 #include <curl/curl.h>
 
-#ifdef __GNUC__
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
-#endif
-
 int main(int argc, char *argv[])
 {
   CURL *curl;
@@ -64,27 +59,29 @@ int main(int argc, char *argv[])
 
   curl_global_init(CURL_GLOBAL_ALL);
 
-  /* Fill in the file upload field */
-  curl_formadd(&formpost,
-               &lastptr,
-               CURLFORM_COPYNAME, "sendfile",
-               CURLFORM_FILE, "postit2-formadd.c",
-               CURLFORM_END);
+  CURL_IGNORE_DEPRECATION(
+    /* Fill in the file upload field */
+    curl_formadd(&formpost,
+                 &lastptr,
+                 CURLFORM_COPYNAME, "sendfile",
+                 CURLFORM_FILE, "postit2-formadd.c",
+                 CURLFORM_END);
 
-  /* Fill in the filename field */
-  curl_formadd(&formpost,
-               &lastptr,
-               CURLFORM_COPYNAME, "filename",
-               CURLFORM_COPYCONTENTS, "postit2-formadd.c",
-               CURLFORM_END);
+    /* Fill in the filename field */
+    curl_formadd(&formpost,
+                 &lastptr,
+                 CURLFORM_COPYNAME, "filename",
+                 CURLFORM_COPYCONTENTS, "postit2-formadd.c",
+                 CURLFORM_END);
 
 
-  /* Fill in the submit field too, even if this is rarely needed */
-  curl_formadd(&formpost,
-               &lastptr,
-               CURLFORM_COPYNAME, "submit",
-               CURLFORM_COPYCONTENTS, "send",
-               CURLFORM_END);
+    /* Fill in the submit field too, even if this is rarely needed */
+    curl_formadd(&formpost,
+                 &lastptr,
+                 CURLFORM_COPYNAME, "submit",
+                 CURLFORM_COPYCONTENTS, "send",
+                 CURLFORM_END);
+  )
 
   curl = curl_easy_init();
   /* initialize custom header list (stating that Expect: 100-continue is not
@@ -96,7 +93,9 @@ int main(int argc, char *argv[])
     if((argc == 2) && (!strcmp(argv[1], "noexpectheader")))
       /* only disable 100-continue header if explicitly requested */
       curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist);
-    curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost);
+    CURL_IGNORE_DEPRECATION(
+      curl_easy_setopt(curl, CURLOPT_HTTPPOST, formpost);
+    )
 
     /* Perform the request, res gets the return code */
     res = curl_easy_perform(curl);
@@ -108,14 +107,13 @@ int main(int argc, char *argv[])
     /* always cleanup */
     curl_easy_cleanup(curl);
 
-    /* then cleanup the formpost chain */
-    curl_formfree(formpost);
+    CURL_IGNORE_DEPRECATION(
+      /* then cleanup the formpost chain */
+      curl_formfree(formpost);
+    )
+
     /* free slist */
     curl_slist_free_all(headerlist);
   }
   return 0;
 }
-
-#ifdef __GNUC__
-#pragma GCC diagnostic pop
-#endif