Re: [FFmpeg-devel] [PATCH] libavformat\file:Fix duplicate JNI symbols

[Zhao Zhili <quinkblack@foxmail.com>]

On 2024/3/24 21:23, Andreas Rheinhardt wrote:
> admin@shaoxia.xyz:
>> From: 联盟少侠 <admin@shaoxia.xyz>
>>
>> The errors indicate that there are multiple definitions of several JNI (Java Native Interface) symbols in the FFmpeg library. Specifically, the linker ld.lld has found duplicate definitions for the following symbols:
>>
>> - ff_jni_get_env
>> - ff_jni_jstring_to_utf_chars
>> - ff_jni_utf_chars_to_jstring
>> - ff_jni_exception_get_summary
>> - ff_jni_exception_check
>> - ff_jni_init_jfields
>> - ff_jni_reset_jfields
>>
>> These symbols are defined in both libavcodec.a and libavformat.a archives, leading to conflicts during the linking process. The duplicates are found in the same source file ffjni.c, but they are being compiled into two different static libraries.
>>
>> To resolve these errors, ensure that each symbol is defined only once across all linked libraries, or if these symbols are required in both libraries, they should be marked as weak symbols to allow the linker to handle them appropriately. Additionally, check for any build script misconfigurations that may be causing the same file to be included in multiple libraries.
>> ---
>>   libavformat/file.c | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/libavformat/file.c b/libavformat/file.c
>> index dd5819c..fa13ae9 100644
>> --- a/libavformat/file.c
>> +++ b/libavformat/file.c
>> @@ -43,7 +43,7 @@
>>   #if CONFIG_ANDROID_CONTENT_PROTOCOL
>>   #include <jni.h>
>>   #include "libavcodec/jni.h"
>> -#include "libavcodec/ffjni.c"
>> +#include "libavcodec/ffjni.h"
>>   #endif
>>   
>>   
> How can this even happen? In case of static builds with the android
> content protocol enabled, libavformat/file.o provides all the symbols
> that libavcodec/ffjni.o also provides. Given that the former is part of
> libavformat.a and this is linked before libavcodec.a, the stuff from the
> former is used and the ffjni.o in libavcodec.a should not be pulled in
> at all.
I guess the error is triggered by creating a shared library from combine 
all static libraries
via -Wl,--whole-archive. It's a common practice to reduce the number of 
shared libraries
in mobile app.
>
> - Andreas
>
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