curl.h: stop defining non-curl `__has_declspec_attribute`

Public curl headers are best not to define 3rd-party or system macros.
Introduce `CURL_HAS_DECLSPEC_ATTRIBUTE` to cover this system macro and
use it.

Detected by test1167 after dropping the indentation:
```
test 1167...[Verify curl prefix of public symbols in header files]

/usr/bin/perl -I. -I.  returned 1, when expecting 0
 1167: exit FAILED
== Contents of files in the log/10/ dir after test 1167
=== Start of file server.cmd
 Testnum 1167
=== End of file server.cmd
=== Start of file stdout1167
 Bad symbols in public header files:
   __has_declspec_attribute(x)
=== End of file stdout1167
```
Ref: https://github.com/curl/curl/actions/runs/13533200900/job/37819784405?pr=16490#step:42:2087

Ref: https://clang.llvm.org/docs/LanguageExtensions.html#has-declspec-attribute
Follow-up to 50482b8c0a2cf5315e66d182998c8fc4901ffb2d #3616
Ref: #16496 (fixing test1167)
Closes #16491

diff --git a/docs/libcurl/symbols-in-versions b/docs/libcurl/symbols-in-versions
index 640344f0e6a2cf220a8d3bbd674895c75f6d6aac..0b566edbc3b19d5614e449d3c288d7039596f794 100644 (file)
--- a/docs/libcurl/symbols-in-versions
+++ b/docs/libcurl/symbols-in-versions
@@ -45,6 +45,7 @@ CURL_GLOBAL_DEFAULT             7.8
 CURL_GLOBAL_NOTHING             7.8
 CURL_GLOBAL_SSL                 7.8
 CURL_GLOBAL_WIN32               7.8.1
+CURL_HAS_DECLSPEC_ATTRIBUTE     8.13.0
 CURL_HET_DEFAULT                7.59.0
 CURL_HTTP_VERSION_1_0           7.9.1
 CURL_HTTP_VERSION_1_1           7.9.1

diff --git a/include/curl/curl.h b/include/curl/curl.h
index 99c57f21690894be86fc2e03993c1ce107c48c60..346872b39d2ee19bd3e156120418c35a2b4dd892 100644 (file)
--- a/include/curl/curl.h
+++ b/include/curl/curl.h
@@ -102,11 +102,6 @@
 #include <sys/time.h>
 #endif
 
-/* Compatibility for non-Clang compilers */
-#ifndef __has_declspec_attribute
-#  define __has_declspec_attribute(x) 0
-#endif
-
 #ifdef  __cplusplus
 extern "C" {
 #endif
@@ -118,11 +113,17 @@ typedef void CURLSH;
  * libcurl external API function linkage decorations.
  */
 
+#ifdef __has_declspec_attribute
+#define CURL_HAS_DECLSPEC_ATTRIBUTE(x) __has_declspec_attribute(x)
+#else
+#define CURL_HAS_DECLSPEC_ATTRIBUTE(x) 0
+#endif
+
 #ifdef CURL_STATICLIB
 #  define CURL_EXTERN
 #elif defined(_WIN32) || \
-     (__has_declspec_attribute(dllexport) && \
-      __has_declspec_attribute(dllimport))
+     (CURL_HAS_DECLSPEC_ATTRIBUTE(dllexport) && \
+      CURL_HAS_DECLSPEC_ATTRIBUTE(dllimport))
 #  if defined(BUILDING_LIBCURL)
 #    define CURL_EXTERN  __declspec(dllexport)
 #  else