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authorFelipe Magno de Almeida <felipe@expertise.dev>2020-12-06 12:26:13 -0300
committerFelipe Magno de Almeida <felipe@expertise.dev>2020-12-06 12:32:34 -0300
commitb01cc905ea5d417030831096b2e81b8a4e823d44 (patch)
tree601dd5457343946e58711daccb6919c46132eb3c
parent3523f106b827ab7696c71a933673623ad2bc85f0 (diff)
eio: Add weak symbol
Summary: Add definition for EAPI_WEAK because this macro will be needed when we change how Eolian generates import/export symbols for the Eio library. = The Rationale = This patch is from a series of patches to rename EAPI symbols to specific library DSOs. EAPI was designed to be able to pass `__attribute__ ((visibility ("default")))` for symbols with GCC, which would mean that even if -fvisibility=hidden was used when compiling the library, the needed symbols would get exported. MSVC __almost__ works like GCC (or mingw) in which you can declare everything as export and it will just work (slower, but it will work). But there's a caveat: global variables will not work the same way for MSVC, but works for mingw and GCC. For global variables (as opposed to functions), MSVC requires correct DSO visibility for MSVC: instead of declaring a symbol as export for everything, you need to declare it as import when importing from another DSO and export when defining it locally. With current EAPI definitions, we get the following example working in mingw and MSVC (observe it doesn't define any global variables as exported symbols). Example 1: dll1: ``` EAPI void foo(void); EAPI void bar() { foo(); } ``` dll2: ``` EAPI void foo() { printf ("foo\n"); } ``` This works fine with API defined as __declspec(dllexport) in both cases and for gcc defining as `__atttribute__((visibility("default")))`. However, the following: Example 2: dll1: ``` EAPI extern int foo; EAPI void foobar(void); EAPI void bar() { foo = 5; foobar(); } ``` dll2: ``` EAPI int foo = 0; EAPI void foobar() { printf ("foo %d\n", foo); } ``` This will work on mingw but will not work for MSVC. And that's why LIBAPI is the only solution that works for MSVC. Co-authored-by: João Paulo Taylor Ienczak Zanette <jpaulotiz@gmail.com> Co-authored-by: Lucas Cavalcante de Sousa <lucks.sousa@gmail.com> Co-authored-by: Ricardo Campos <ricardo.campos@expertise.dev> Reviewers: jptiz, lucas, vtorri, woohyun Reviewed By: vtorri Subscribers: cedric, #reviewers, #committers Tags: #efl Differential Revision: https://phab.enlightenment.org/D12201
-rw-r--r--src/lib/eio/Eio.h8
1 files changed, 8 insertions, 0 deletions
diff --git a/src/lib/eio/Eio.h b/src/lib/eio/Eio.h
index fb0fc64813..f72529e6e0 100644
--- a/src/lib/eio/Eio.h
+++ b/src/lib/eio/Eio.h
@@ -36,6 +36,10 @@
36# undef EAPI 36# undef EAPI
37#endif 37#endif
38 38
39#ifdef EAPI_WEAK
40# undef EAPI_WEAK
41#endif
42
39#ifdef _WIN32 43#ifdef _WIN32
40# ifdef EFL_BUILD 44# ifdef EFL_BUILD
41# ifdef DLL_EXPORT 45# ifdef DLL_EXPORT
@@ -46,15 +50,19 @@
46# else 50# else
47# define EAPI __declspec(dllimport) 51# define EAPI __declspec(dllimport)
48# endif 52# endif
53# define EAPI_WEAK
49#else 54#else
50# ifdef __GNUC__ 55# ifdef __GNUC__
51# if __GNUC__ >= 4 56# if __GNUC__ >= 4
52# define EAPI __attribute__ ((visibility("default"))) 57# define EAPI __attribute__ ((visibility("default")))
58# define EAPI_WEAK __attribute__ ((weak))
53# else 59# else
54# define EAPI 60# define EAPI
61# define EAPI_WEAK
55# endif 62# endif
56# else 63# else
57# define EAPI 64# define EAPI
65# define EAPI_WEAK
58# endif 66# endif
59#endif 67#endif
60 68