GCC -rdynamic不能与静态库一起工作 [英] GCC -rdynamic not working with static libraries
问题描述
为什么-rdynamic不在.a文件中导出符号,而是在.o文件中导出符号?
我有一个应用程序和一个插件一个.so文件。主应用程序使用一系列目标文件和一个静态库链接,如下所示:
CXXFLAGS = $(CXXFLAGS_COMMON) - rdynamic
STATICLIBS = ../Utilities/Utilities.a
...
全部:
$(CXX)$(CXXFLAGS)-o $(样本) main.o $(STATICLIBS)$(SHAREDLIBS)$(INCLUDES)
在这种情况下,Utilities.a中的符号不会被导出(即objdump - t a.out | grep symbol为空)。 如果我使用ar x来提取.a中的.o文件并仅使用链接。 o,那么这些符号会被插件导出并找到(如果您想知道的话,这些插件会加载dlopen)。 我试过使用-Wl,-export - 动态但没有成功。 我有一个解决方法,正如提到的,但我仍然想明白我缺少的东西。通常情况下,链接器只包含静态存档的那些部分(
.a
强制链接器包含 .a $ c的全部内容$ c>文件,您可以使用
- 整个存档
链接器选项(所以 -Wl, - 整个存档$ c $请注意,
-Wl, - whole-archive
是位置指定的,在命令行上敏感 - 它只会影响命令行中的 .a
文件。如果还有更多的静态档案不需要完全包含,那么它的效果可能会随后被 -Wl, - no-whole-archive
关掉。
所以,比如用你的命令:
$(CXX )$(CXXFLAGS)-o $(SAMPLE)main.o -Wl, - whole-archive $(STATICLIBS)-Wl, - no-whole-archive $(SHAREDLIBS)$(INCLUDES)
Why is -rdynamic not exporting the symbols in .a files but is exporting the symbols in .o files ?
I have an app and a plug-in in a .so file. The main app is linked using a series of object files and one static library, like this:
CXXFLAGS = $(CXXFLAGS_COMMON) -rdynamic
STATICLIBS = ../Utilities/Utilities.a
...
all:
$(CXX) $(CXXFLAGS) -o $(SAMPLE) main.o $(STATICLIBS) $(SHAREDLIBS) $(INCLUDES)
(CXX is g++ 4.5.2 on Ubunut, I use mainly -std=c++Ox for compilation)
In this case, the symbols in Utilities.a are not exported (i.e. "objdump -t a.out | grep symbol" is empty).
If I use "ar x" to extract the .o files in the .a and link using only the .o's, then the symbols are exported and found by the plug-ins (that are loaded with dlopen in case you wondered).
I have tried using -Wl,-export-dynamic but without success.
I do have a workaround, as mentionned, but I'd still wish to understand what I am missing. Thanks in advance !
Normally, the linker only includes those parts of static archives (.a
files) which are referenced.
To force the linker to include the entire contents of a .a
file, you can use the --whole-archive
linker option (so -Wl,--whole-archive
on the gcc command line).
Note that -Wl,--whole-archive
is position-sensitive on the command line — it only affects .a
files following it on the command line. Its effect may be subsequently turned off using -Wl,--no-whole-archive
, if there are further static archives which you don't want to be completely included.
So, for instance, with your command:
$(CXX) $(CXXFLAGS) -o $(SAMPLE) main.o -Wl,--whole-archive $(STATICLIBS) -Wl,--no-whole-archive $(SHAREDLIBS) $(INCLUDES)
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