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Don't define SDL_ELF_NOTE_DLOPEN when compiler does not support variadic macro's #14245

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Don't define SDL_ELF_NOTE_DLOPEN when compiler does not support variadic macro's #14245

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dc442ef
dlopennote: update documentation and internal variable names
madebr Oct 14, 2025
5e65ffc
dlopennote: don't define SDL_ELF_NOTE_DLOPEN when variadic macro's ar…
madebr Oct 14, 2025
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84 changes: 43 additions & 41 deletions include/SDL3/SDL_dlopennote.h
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Original file line number Diff line number Diff line change
Expand Up @@ -32,21 +32,23 @@
* this CMake snippet to check for support:
*
* ```cmake
* set(CHECK_ELF_DLNOTES_SRC [==[
* #ifndef __ELF__
* ELF DL notes is only supported on ELF platforms
* #endif
* __attribute__ ((used,aligned(4),section(".note.dlopen"))) static const struct {
* struct { int a; int b; int c; } hdr; char name[4]; __attribute__((aligned(4))) char json[24];
* } dlnote = { { 4, 0x407c0c0aU, 16 }, "FDO", "[\\"a\\":{\\"a\\":\\"1\\",\\"b\\":\\"2\\"}]" };
* int main(int argc, char *argv[]) {
* return argc + dlnote.hdr.a;
* }
* ]==])
* check_c_source_compiles("${CHECK_ELF_DLNOTES_SRC}" COMPILER_SUPPORTS_ELFNOTES)
* if(NOT COMPILER_SUPPORTS_ELFNOTES)
* set(SDL_DISABLE_DLOPEN_NOTES TRUE)
* endif()
* include(CheckCSourceCompiles)
* find_package(SDL3 REQUIRED CONFIG COMPONENTS Headers)
* list(APPEND CMAKE_REQUIRED_LIBRARIES SDL3::Headers)
* check_c_source_compiles([==[
* #include <SDL3/SDL_dlopennote.h>
* SDL_ELF_NOTE_DLOPEN("sdl-video",
* "Support for video through SDL",
* SDL_ELF_NOTE_DLOPEN_PRIORITY_SUGGESTED,
* "libSDL-1.2.so.0", "libSDL-2.0.so.0", "libSDL3.so.0"
* );
* int main(int argc, char *argv[]) {
* return argc + argv[0][1];
* }
* ]==] COMPILER_SUPPORTS_SDL_ELF_NOTE_DLOPEN)
* if(NOT COMPILER_SUPPORTS_SDL_ELF_NOTE_DLOPEN)
* add_compile_definitions(-DSDL_DISABLE_DLOPEN_NOTE)
* endif()
* ```
*/

Expand Down Expand Up @@ -141,33 +143,34 @@
#define SDL_ELF_NOTE_INTERNAL(json, variable_name) \
SDL_ELF_NOTE_INTERNAL2(json, variable_name)

#define SDL_SONAME_ARRAY1(N1) "[\"" N1 "\"]"
#define SDL_SONAME_ARRAY2(N1,N2) "[\"" N1 "\",\"" N2 "\"]"
#define SDL_SONAME_ARRAY3(N1,N2,N3) "[\"" N1 "\",\"" N2 "\",\"" N3 "\"]"
#define SDL_SONAME_ARRAY4(N1,N2,N3,N4) "[\"" N1 "\",\"" N2 "\",\"" N3 "\",\"" N4 "\"]"
#define SDL_SONAME_ARRAY5(N1,N2,N3,N4,N5) "[\"" N1 "\",\"" N2 "\",\"" N3 "\",\"" N4 "\",\"" N5 "\"]"
#define SDL_SONAME_ARRAY6(N1,N2,N3,N4,N5,N6) "[\"" N1 "\",\"" N2 "\",\"" N3 "\",\"" N4 "\",\"" N5 "\",\"" N6 "\"]"
#define SDL_SONAME_ARRAY7(N1,N2,N3,N4,N5,N6,N7) "[\"" N1 "\",\"" N2 "\",\"" N3 "\",\"" N4 "\",\"" N5 "\",\"" N6 "\",\"" N7 "\"]"
#define SDL_SONAME_ARRAY8(N1,N2,N3,N4,N5,N6,N7,N8) "[\"" N1 "\",\"" N2 "\",\"" N3 "\",\"" N4 "\",\"" N5 "\",\"" N6 "\",\"" N7 "\",\"" N8 "\"]"
#define SDL_SONAME_ARRAY_GET(N1,N2,N3,N4,N5,N6,N7,N8,NAME,...) NAME
#define SDL_SONAME_ARRAY(...) \
SDL_SONAME_ARRAY_GET(__VA_ARGS__, \
SDL_SONAME_ARRAY8, \
SDL_SONAME_ARRAY7, \
SDL_SONAME_ARRAY6, \
SDL_SONAME_ARRAY5, \
SDL_SONAME_ARRAY4, \
SDL_SONAME_ARRAY3, \
SDL_SONAME_ARRAY2, \
SDL_SONAME_ARRAY1 \
#define SDL_DLNOTE_JSON_ARRAY1(N1) "[\"" N1 "\"]"
#define SDL_DLNOTE_JSON_ARRAY2(N1,N2) "[\"" N1 "\",\"" N2 "\"]"
#define SDL_DLNOTE_JSON_ARRAY3(N1,N2,N3) "[\"" N1 "\",\"" N2 "\",\"" N3 "\"]"
#define SDL_DLNOTE_JSON_ARRAY4(N1,N2,N3,N4) "[\"" N1 "\",\"" N2 "\",\"" N3 "\",\"" N4 "\"]"
#define SDL_DLNOTE_JSON_ARRAY5(N1,N2,N3,N4,N5) "[\"" N1 "\",\"" N2 "\",\"" N3 "\",\"" N4 "\",\"" N5 "\"]"
#define SDL_DLNOTE_JSON_ARRAY6(N1,N2,N3,N4,N5,N6) "[\"" N1 "\",\"" N2 "\",\"" N3 "\",\"" N4 "\",\"" N5 "\",\"" N6 "\"]"
#define SDL_DLNOTE_JSON_ARRAY7(N1,N2,N3,N4,N5,N6,N7) "[\"" N1 "\",\"" N2 "\",\"" N3 "\",\"" N4 "\",\"" N5 "\",\"" N6 "\",\"" N7 "\"]"
#define SDL_DLNOTE_JSON_ARRAY8(N1,N2,N3,N4,N5,N6,N7,N8) "[\"" N1 "\",\"" N2 "\",\"" N3 "\",\"" N4 "\",\"" N5 "\",\"" N6 "\",\"" N7 "\",\"" N8 "\"]"
#define SDL_DLNOTE_JSON_ARRAY_GET(N1,N2,N3,N4,N5,N6,N7,N8,NAME,...) NAME
#define SDL_DLNOTE_JSON_ARRAY(...) \
SDL_DLNOTE_JSON_ARRAY_GET( \
__VA_ARGS__, \
SDL_DLNOTE_JSON_ARRAY8, \
SDL_DLNOTE_JSON_ARRAY7, \
SDL_DLNOTE_JSON_ARRAY6, \
SDL_DLNOTE_JSON_ARRAY5, \
SDL_DLNOTE_JSON_ARRAY4, \
SDL_DLNOTE_JSON_ARRAY3, \
SDL_DLNOTE_JSON_ARRAY2, \
SDL_DLNOTE_JSON_ARRAY1 \
)(__VA_ARGS__)

/* Create "unique" variable name using __LINE__,
* so creating elf notes on the same line is not supported
* so creating multiple elf notes on the same line is not supported
*/
#define SDL_ELF_NOTE_JOIN2(A,B) A##B
#define SDL_ELF_NOTE_JOIN(A,B) SDL_ELF_NOTE_JOIN2(A,B)
#define SDL_ELF_NOTE_UNIQUE_NAME SDL_ELF_NOTE_JOIN(s_SDL_dlopen_note_, __LINE__)
#define SDL_DLNOTE_JOIN2(A,B) A##B
#define SDL_DLNOTE_JOIN(A,B) SDL_DLNOTE_JOIN2(A,B)
#define SDL_DLNOTE_UNIQUE_NAME SDL_DLNOTE_JOIN(s_SDL_dlopen_note_, __LINE__)

/**
* Note that your application has dynamic shared library dependencies.
Expand Down Expand Up @@ -206,8 +209,8 @@
"[{\"feature\":\"" feature \
"\",\"description\":\"" description \
"\",\"priority\":\"" priority \
"\",\"soname\":" SDL_SONAME_ARRAY(__VA_ARGS__) "}]", \
SDL_ELF_NOTE_UNIQUE_NAME)
"\",\"soname\":" SDL_DLNOTE_JSON_ARRAY(__VA_ARGS__) "}]", \
SDL_DLNOTE_UNIQUE_NAME)

#elif defined(__GNUC__) && __GNUC__ < 3

Expand All @@ -216,7 +219,6 @@
#elif defined(_MSC_VER) && _MSC_VER < 1400

/* Variadic macros are not supported */
#define SDL_ELF_NOTE_DLOPEN

#else

Expand Down
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