chore: Statically link OpenMP into the cracker fun util on Windows

For some reason even with -DCMAKE_EXE_LINKER_FLAGS="-static" specified,
CMake still links OpenMP dynamically, even though it links other libs
statically, e.g. -pthread.

Author: nurupo

other/docker/windows/build_toxcore.sh

@@ -66,6 +66,10 @@ build() {
     TOXCORE_CFLAGS="-fno-asynchronous-unwind-tables"
   fi
 
+  # Patch CMakeLists.txt to make cracker.exe statically link against OpenMP. For some reason
+  # -DCMAKE_EXE_LINKER_FLAGS="-static" doesn't do it.
+  sed -i "s|OpenMP::OpenMP_C)|$(realpath -- /usr/lib/gcc/"$WINDOWS_TOOLCHAIN"/*-win32/libgomp.a) \${CMAKE_THREAD_LIBS_INIT})\ntarget_compile_options(cracker PRIVATE -fopenmp)|g" ../other/fun/CMakeLists.txt
+
   # Silly way to bypass a shellharden check
   read -ra EXTRA_CMAKE_FLAGS_ARRAY <<<"$EXTRA_CMAKE_FLAGS"
   CFLAGS="$CFLAGS $TOXCORE_CFLAGS" \

other/fun/CMakeLists.txt

@@ -42,12 +42,12 @@ add_executable(cracker_simple cracker_simple.c)
 target_link_libraries(cracker_simple PRIVATE misc_tools)
 target_link_sodium(cracker_simple)
 
-# MSVC doesn't support OpenMP
-if(NOT MSVC)
-  find_package(OpenMP)
-  if(OpenMP_C_FOUND)
-    add_executable(cracker cracker.c)
-    target_link_sodium(cracker)
-    target_link_libraries(cracker PRIVATE OpenMP::OpenMP_C)
-  endif()
+find_package(OpenMP)
+if(OpenMP_C_FOUND)
+  add_executable(cracker cracker.c)
+  target_link_libraries(cracker PRIVATE OpenMP::OpenMP_C)
+  target_link_sodium(cracker)
+else()
+  add_executable(cracker cracker.c)
+  target_link_sodium(cracker)
 endif()

other/fun/cracker.c

@@ -33,6 +33,7 @@
 #include <omp.h>
 #define NUM_THREADS() ((unsigned) omp_get_max_threads())
 #else
+#pragma message("Being built without OpenMP support -- the program will utilize a single thread only.")
 #define NUM_THREADS() (1U)
 #endif
 
@@ -112,8 +113,9 @@ static size_t match_hex_prefix(const uint8_t *key, const uint8_t *prefix, size_t
 static void cracker_core(uint64_t range_start, uint64_t range_end, uint64_t range_offs, uint64_t priv_key_shadow[4],
                          uint32_t *longest_match, uint8_t hex_prefix[MAX_CRACK_BYTES], size_t prefix_chars_len)
 {
+#if defined(_OPENMP)
     #pragma omp parallel for firstprivate(priv_key_shadow) shared(longest_match, range_start, range_end, range_offs, hex_prefix, prefix_chars_len) schedule(static) default(none)
-
+#endif
     for (uint64_t batch = range_start; batch < range_end; ++batch) {
         uint8_t *priv_key = (uint8_t *) priv_key_shadow;
         /*
@@ -134,14 +136,19 @@ static void cracker_core(uint64_t range_start, uint64_t range_end, uint64_t rang
 
         // Global compare and update
         uint32_t l_longest_match;
+#if defined(_OPENMP)
         #pragma omp atomic read
+#endif
         l_longest_match = *longest_match;
 
         if (matching > l_longest_match) {
+#if defined(_OPENMP)
             #pragma omp atomic write
+#endif
             *longest_match = matching;
-
+#if defined(_OPENMP)
             #pragma omp critical
+#endif
             {
                 printf("%u chars matching: \n", matching);
                 printf("Public key: ");