[Vm-dev] [Off-Topic] linking exported symbols into shared lib

[Nicolas Cellier]

And maybe another good hit
https://www.gnu.org/software/gnulib/manual/html_node/Exported-Symbols-of-Shared-Libraries.html

2017-11-06 19:29 GMT+01:00 Nicolas Cellier <
nicolas.cellier.aka.nice at gmail.com>:

> Maybe google gcc export all symbols
> a workaround would be -Wl,--export-all-symbols or something like that...
> I find the end of http://anadoxin.org/blog/control-over-symbol-exports-
> in-gcc.html interesting though it's the inverse problem
>
> 2017-11-06 19:08 GMT+01:00 Ben Coman <btc at openinworld.com>:
>
>>
>>
>> $ nm -A fpdfview.o | grep FPDF_Init
>> fpdfview.o:0000000000000000  T   FPDF_InitLibrary
>> fpdfview.o:0000000000000000  T   FPDF_InitLibraryWithConfig
>> fpdfview.o:0000000000000000   t   FPDF_InitLibraryWithConfig.part.47
>>
>>
>> IIUC, the capital "T" means the "FPDF_InitLibrary" symbol is exported and
>> available for another program to link against. Browsing around, object
>> files are composed into a shared library like this...
>>
>> $ g++ -fPIC -shared -o libmypdf.so fpdfview.o
>>
>>
>> but now the "FPDF_InitLibrary" symbol shows as internal and I can't link
>> against it.
>>
>> $ nm -A libmypdf.so | grep FPDF_Init
>> libmypdf.so:0000000000003e60  t   FPDF_InitLibrary
>> libmypdf.so:0000000000003e80  t   FPDF_InitLibraryWithConfig
>> libmypdf.so:00000000000031f0   t   FPDF_InitLibraryWithConfig.part.47
>>
>>
>> Here is my makefile...
>>
>> INC_DIR= -I ./public
>> LIB_DIR= -L ./out
>> STD_LIBS= -lpthread -lm -lc -lstdc++
>> PDF_LIBS= -lmypdfium
>> default:
>>         gcc -o first first.c ${INC_DIR} ${LIB_DIR} ${PDF_LIBS} ${STD_LIBS}
>>
>> So I know it finds the library, since if I change its name the linker
>> complains it can't find the file.
>>
>>
>>
>> I don't think the following adds useful extra info, but for
>> completeness... The header file fpdfview.h has...
>>
>> #if defined(_WIN32) && defined(FPDFSDK_EXPORTS)
>> // On Windows system, functions are exported in a DLL
>> #define FPDF_EXPORT __declspec(dllexport)
>> #define FPDF_CALLCONV __stdcall
>> #else
>> #define FPDF_EXPORT
>> #define FPDF_CALLCONV
>> #endif
>>
>> #ifdef __cplusplus
>> extern "C" {
>> #endif
>>
>> FPDF_EXPORT void FPDF_CALLCONV FPDF_InitLibrary();
>>
>> #ifdef __cplusplus
>> }
>> #endif
>>
>>
>>
>>
>>
>>
>
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