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authorFelipe Magno de Almeida <felipe@expertise.dev>2020-12-04 10:27:52 -0300
committerFelipe Magno de Almeida <felipe@expertise.dev>2020-12-04 10:35:35 -0300
commit8d18009419d5ea09f15d9fa27499fcf36123c057 (patch)
tree021e0cd02b472588d7323e213f03941c28ad3068 /src/modules/ecore/system
parent650578b57368babc6600d65549b62dae9b9e6423 (diff)
eolian: Add -e parameter to pass export symbol to eolian generatorHEADmaster
Summary: Eolian generator must have a parameter so it can generate the correct symbol export/import macro for the API generated. This makes it possible to define the symbols as being local to a single DSO without the need to guard the generated headers or generated source files with #define and #undef preprocessor statements. = 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: q66, vtorri, woohyun, jptiz, lucas Reviewed By: vtorri, lucas Subscribers: cedric, #reviewers, #committers Tags: #efl Differential Revision: https://phab.enlightenment.org/D12197
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