At least ws_server.c contains code, which is not supported on Android > NDK 23 about civetweb HOT 5 OPEN

Interesting that Android removed __sync_add_and_fetch. Did they offer any replacement for this?

https://github.com/civetweb/civetweb/blob/master/examples/ws_server/ws_server.c#L48 is only an example code, not part of the portable web server core. This example probably only runs on Linux, also not on Windows. It could be changed to use #if defined(WIN32) ... #elif defined(OSX) ... #elif defined(LINUX) ... #elif define(ANDROID) && (NDK_Version>23) ... #elif define(ANDROID) && (NDK_Version<=23) ... #else .... #endif and using a pthread_mutex or CriticalSession or any other operating system or library depending lock mechanism.

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android/ndk#1231 ?

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There I read the android development switched from GCC to CLANG.
But __sync_add_and_fetch is provided by clang, provided you use a recent version (llvm/llvm-project#62084).

Although, it could be the new version needs __atomic_add_fetch instead of the older __sync_add_and_fetch - unfortunately this change will break the build for older compilers.

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Android used to use __snyc_add_and_fetch (https://android.googlesource.com/platform/art/+/2ec6520/runtime/atomic.h)

Now it is probably int32_t android_atomic_add(int32_t value, volatile int32_t* addr); (https://android.googlesource.com/platform/system/core/+/ac322da/include/cutils/atomic.h#41).
I cannot really find a good source on this and I did not download the new NDK yet - this may take a while to check.

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But I also believe that all NDK versions should work with all SDK versions, so in this sense an upgrade just for this library is not necessary. However, then it's not possible to mix it with libraries that work with NDK >= 23.

The below snippet suggests that the replacement is android_atomic_inc(&value_) + 1;

https://android.googlesource.com/platform/art/+/b122a4b%5E%21/

-  int32_t operator++() {
-    return android_atomic_inc(&value_) + 1;
+  int32_t operator++() {  // Prefix operator.
+    return __sync_add_and_fetch(&value_, 1);  // Return new value.
   }

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