WIP: visibility example for cmake

Author: purpleKarrot

.github/workflows/ci.yml

@@ -615,7 +615,7 @@ jobs:
         run: cmake -E env CFLAGS="/WX ${{ matrix.configuration.cpp_flags }}" cmake -B build -DSECP256K1_ENABLE_MODULE_RECOVERY=ON -DSECP256K1_BUILD_EXAMPLES=ON ${{ matrix.configuration.cmake_options }}
 
       - name: Build
-        run: cmake --build build --config RelWithDebInfo -- /p:UseMultiToolTask=true /maxCpuCount
+        run: cmake --build build --config RelWithDebInfo --verbose -- /p:UseMultiToolTask=true /maxCpuCount
 
       - name: Binaries info
         # Use the bash shell included with Git for Windows.

include/secp256k1.h

@@ -121,45 +121,21 @@ typedef int (*secp256k1_nonce_function)(
 #endif
 
 /* Symbol visibility. */
-#if defined(_WIN32)
-  /* GCC for Windows (e.g., MinGW) accepts the __declspec syntax
-   * for MSVC compatibility. A __declspec declaration implies (but is not
-   * exactly equivalent to) __attribute__ ((visibility("default"))), and so we
-   * actually want __declspec even on GCC, see "Microsoft Windows Function
-   * Attributes" in the GCC manual and the recommendations in
-   * https://gcc.gnu.org/wiki/Visibility. */
-# if defined(SECP256K1_BUILD)
-#  if defined(DLL_EXPORT) || defined(SECP256K1_DLL_EXPORT)
-    /* Building libsecp256k1 as a DLL.
-     * 1. If using Libtool, it defines DLL_EXPORT automatically.
-     * 2. In other cases, SECP256K1_DLL_EXPORT must be defined. */
-#   define SECP256K1_API extern __declspec (dllexport)
-#  else
-    /* Building libsecp256k1 as a static library on Windows.
-     * No declspec is needed, and so we would want the non-Windows-specific
-     * logic below take care of this case. However, this may result in setting
-     * __attribute__ ((visibility("default"))), which is supposed to be a noop
-     * on Windows but may trigger warnings when compiling with -flto due to a
-     * bug in GCC, see
-     * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=116478 . */
-#   define SECP256K1_API extern
-#  endif
-  /* The user must define SECP256K1_STATIC when consuming libsecp256k1 as a static
-   * library on Windows. */
-# elif !defined(SECP256K1_STATIC)
-   /* Consuming libsecp256k1 as a DLL. */
-#  define SECP256K1_API extern __declspec (dllimport)
-# endif
+#if defined(_WIN32) || defined(__CYGWIN__)
+#  define SECP256K1_EXPORT __declspec(dllexport)
+#  define SECP256K1_IMPORT __declspec(dllimport)
+#else
+#  define SECP256K1_EXPORT __attribute__((visibility("default")))
+#  define SECP256K1_IMPORT __attribute__((visibility("default")))
 #endif
 #ifndef SECP256K1_API
-/* All cases not captured by the Windows-specific logic. */
-# if defined(__GNUC__) && (__GNUC__ >= 4) && defined(SECP256K1_BUILD)
-   /* Building libsecp256k1 using GCC or compatible. */
-#  define SECP256K1_API extern __attribute__ ((visibility ("default")))
-# else
-   /* Fall back to standard C's extern. */
-#  define SECP256K1_API extern
-# endif
+#  if defined(SECP256K1_STATIC)
+#    define SECP256K1_API extern
+#  elif defined(SECP256K1_BUILD)
+#    define SECP256K1_API extern SECP256K1_EXPORT
+#  else
+#    define SECP256K1_API extern SECP256K1_IMPORT
+#  endif
 #endif
 
 /* Warning attributes

src/CMakeLists.txt

@@ -70,11 +70,9 @@ if(SECP256K1_ASM STREQUAL "arm32")
   target_link_libraries(secp256k1_asm INTERFACE secp256k1_asm_arm)
 endif()
 
-if(WIN32)
-  # Define our export symbol only for shared libs.
-  set_target_properties(secp256k1 PROPERTIES DEFINE_SYMBOL SECP256K1_DLL_EXPORT)
-  target_compile_definitions(secp256k1 INTERFACE $<$<NOT:$<BOOL:${BUILD_SHARED_LIBS}>>:SECP256K1_STATIC>)
-endif()
+# When building a static libary, SECP256K1_STATIC must be defined both for itself and downstream.
+target_compile_definitions(secp256k1 PUBLIC $<$<STREQUAL:$<TARGET_PROPERTY:TYPE>,STATIC_LIBRARY>:SECP256K1_STATIC>)
+set_target_properties(secp256k1 PROPERTIES C_VISIBILITY_PRESET hidden)
 
 # Object libs don't know if they're being built for a shared or static lib.
 # Grab the PIC property from secp256k1 which knows.