差異處
這裏顯示兩個版本的差異處。
| Both sides previous revision 前次修改 下次修改 | 前次修改 | ||
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java:jna:c_so的undefined_symbol問題 [2017/03/16 11:03] tony [Problem] |
java:jna:c_so的undefined_symbol問題 [2023/06/25 09:48] (目前版本) |
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| 行 1: | 行 1: | ||
| + | {{tag>jna cpp mangling}} | ||
| ====== c++ so的undefined symbol問題 ====== | ====== c++ so的undefined symbol問題 ====== | ||
| ===== Problem ===== | ===== Problem ===== | ||
| 行 31: | 行 32: | ||
| } | } | ||
| </file> | </file> | ||
| - | 在執行後會出現以下錯誤: (請記得要設定環境變數LD_LI) | + | 在執行後會出現以下錯誤: (請記得要設定環境變數LD_LIBRARY_PATH) |
| <code> | <code> | ||
| Exception in thread "main" java.lang.UnsatisfiedLinkError: Error looking up function 'test': /opt/test/libtest.so: undefined symbol: test | Exception in thread "main" java.lang.UnsatisfiedLinkError: Error looking up function 'test': /opt/test/libtest.so: undefined symbol: test | ||
| 行 42: | 行 43: | ||
| at com.supermicro.ssm.common.jna.Tester.main(Tester.java:15) | at com.supermicro.ssm.common.jna.Tester.main(Tester.java:15) | ||
| </code> | </code> | ||
| + | ===== How to resolve? ===== | ||
| + | 在我透過gcc編成so時，這問題是沒發生過的。到底兩者差在哪呢? 因此我也透過gcc指令去產生so檔來做比較: | ||
| + | <code bash> | ||
| + | gcc -shared -fPIC -o libtest.so test.c | ||
| + | </code> | ||
| + | 接著使用nm -D去確認dynamic symbol的差異:\\ | ||
| + | {{:java:jna:jna_dump_d_symbol_between_cpp_and_c.png|}}\\ | ||
| + | 發現是由於g++所產生的symbol參雜了其它東西，這是由於C++為了function overloading使用了[[https://en.wikipedia.org/wiki/Name_mangling|Name mangling]]的技術。 | ||
| + | 為了避免這個問題，我們可以透過在function宣告extern "C": | ||
| + | <file cpp test.c> | ||
| + | extern "C" int test() | ||
| + | { | ||
| + | return 0; | ||
| + | } | ||
| + | </file> | ||
| + | 此時可以透過nm -D指令去確認編譯出來的so檔，是否保有原本的symbol名稱，與確認JNA已可正常使用。 | ||
| + | ===== Reference ===== | ||
| + | * [[http://stackoverflow.com/questions/31541451/create-shared-library-from-cpp-files-and-static-library-with-g|Create shared library from cpp files and static library with g++]] | ||
| + | * [[http://stackoverflow.com/questions/34732/how-do-i-list-the-symbols-in-a-so-file|How do I list the symbols in a .so file?]] | ||
| + | * [[http://stackoverflow.com/questions/15965592/calling-a-c-dll-method-from-java-using-jna-and-avoiding-method-name-mangling|Calling a C++ dll method from Java using JNA and avoiding Method Name Mangling]] | ||
| + | * [[https://puremonkey2010.blogspot.tw/2010/08/c-cextern-c.html|extern "C"的意義]] | ||
| + | * [[http://b8807053.pixnet.net/blog/post/3612202-c%2B%2B%E4%B8%ADextern-c%E5%90%AB%E7%BE%A9%E6%B7%B1%E5%B1%A4%E6%8E%A2%E7%B4%A2|C++中extern C含義深層探索]] | ||
| + | * [[https://en.wikipedia.org/wiki/Name_mangling|Name Mangling]] | ||
| + | |||
| + | ===== ===== | ||
| + | ---- | ||
| + | \\ | ||
| + | ~~DISQUS~~ | ||
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| + | |||
