为什么我的C ++输出的可执行文件是这么大？ [英] why my C++ output executable is so big?
问题描述
我有一个非常简单的C ++项目，该项目采用的boost ::正则表达式库。我得到的输出大小3.5MB。据我所知，我静态链接所有的提振.cpp文件，包括所有的函数/方法。也许有可能以某种方式来指导我的链接使用从boost只在必要的元素，不是所有的人？谢谢你。
I have a rather simple C++ project, which uses boost::regex library. The output I'm getting is 3.5Mb in size. As I understand I'm statically linking all boost .CPP files, including all functions/methods. Maybe it's possible somehow to instruct my linker to use only necessary elements from boost, not all of them? Thanks.
$ c++ —version
i686-apple-darwin10-g++-4.2.1 (GCC) 4.2.1 (Apple Inc. build 5659)
这是什么尺寸说：
$ size a.out
__TEXT __DATA __OBJC others dec hex
1556480 69632 0 4296504912 4298131024 100304650
我试过条：
$ ls -al
... 3946688 May 21 13:20 a.out
$ strip a.out
$ ls -al
... 3847248 May 21 13:20 a.out
PS。这就是我的code组织（也许这是问题的主因）：
ps. This is how my code is organized (maybe this is the main cause of the problem):
// file MyClass.h
class MyClass {
void f();
};
#include "MyClassImpl.h"
// file MyClassImpl.h
void MyClass::f() {
// implementation...
}
// file main.cpp
#include "MyClass.h"
int main(int ac, char** av) {
MyClass c;
c.f();
}
你怎么想的？
推荐答案
你与调试符号编译启用？这可以解释为大小的很大一部分。另外你是如何确定的二进制文件的大小？您使用的是假设你使用的是类UNIX平台直 的ls -l </ code> 或 尺寸 命令。如果二进制包含调试符号两个可以给大大不同的结果。例如，这里正在建设的 Boost.Regex <当我得到的结果/ A><一个href=\"http://www.boost.org/doc/libs/1_33_1/libs/regex/example/snippets/credit_card_example.cpp\">credit_card_example.cpp\"例子。
Did you compile with debugging symbols enabled? That could account for a large portion of the size. Also how are you determining the size of the binary? Assuming you're on a UNIX-like platform are you using a straight "ls -l" or the "size" command. The two could give greatly different results if the binary contains debugging symbols. For example, here are the results I get when building the Boost.Regex "credit_card_example.cpp" example.
$ g++ -g -O3 foo.cpp -lboost_regex-mt
$ ls -l a.out
-rwxr-xr-x 1 void void 483801 2010-05-20 10:36 a.out
$ size a.out
text data bss dec hex filename
73330 492 336 74158 121ae a.out
类似的结果发生在刚生成的对象文件：
Similar results occur when just generating the object file:
$ g++ -c -g -O3 foo.cpp
$ ls -l foo.o
-rw-r--r-- 1 void void 622476 2010-05-20 10:40 foo.o
$ size foo.o
text data bss dec hex filename
49119 4 40 49163 c00b foo.o
修改：增加了一些静态链接结果...
EDIT: Added some static linking results ...
下面是当静态链接的二进制尺寸。这是更接近你在说什么：
Here's the binary size when statically linking. It's closer to what you're getting:
$ g++ -static -g -O3 foo.cpp -lboost_regex-mt -lpthread
$ ls -l a.out
-rwxr-xr-x 1 void void 2019905 2010-05-20 11:16 a.out
$ size a.out
text data bss dec hex filename
1204517 5184 41976 1251677 13195d a.out
这也有可能是很多大尺寸是从其他图书馆来Boost.Regex库依赖。在我的Ubuntu框中，Boost.Regex共享库的依赖关系如下：
It's also possible that much of the large size is coming from other libraries the Boost.Regex library depends on. On my Ubuntu box, the dependencies for the Boost.Regex shared library are the following:
$ ldd /usr/lib/libboost_regex-mt.so.1.38.0
linux-gate.so.1 => (0x0053f000)
libicudata.so.40 => /usr/lib/libicudata.so.40 (0xb6a38000)
libicui18n.so.40 => /usr/lib/libicui18n.so.40 (0x009e0000)
libicuuc.so.40 => /usr/lib/libicuuc.so.40 (0x00672000)
librt.so.1 => /lib/tls/i686/cmov/librt.so.1 (0x001e2000)
libstdc++.so.6 => /usr/lib/libstdc++.so.6 (0x001eb000)
libm.so.6 => /lib/tls/i686/cmov/libm.so.6 (0x00110000)
libgcc_s.so.1 => /lib/libgcc_s.so.1 (0x009be000)
libpthread.so.0 => /lib/tls/i686/cmov/libpthread.so.0 (0x00153000)
libc.so.6 => /lib/tls/i686/cmov/libc.so.6 (0x002dd000)
/lib/ld-linux.so.2 (0x00e56000)
借助 ICU 库可以得到相当大。除了调试符号，也许他们是主要贡献者二进制文件的大小。此外，在静态连接的情况下，它看起来像Boost.Regex库本身是由大对象文件：
The ICU libraries can get quite large. Besides debugging symbols, perhaps they are the primary contributors to the size of your binary. Furthermore, in the statically linked case, it looks like the Boost.Regex library itself is comprised of large object files:
$ size --totals /usr/lib/libboost_regex-mt.a | sort -n
0 0 0 0 0 regex_debug.o (ex /usr/lib/libboost_regex-mt.a)
0 0 0 0 0 usinstances.o (ex /usr/lib/libboost_regex-mt.a)
0 0 0 0 0 w32_regex_traits.o (ex /usr/lib/libboost_regex-mt.a)
text data bss dec hex filename
435 0 0 435 1b3 regex_raw_buffer.o (ex /usr/lib/libboost_regex-mt.a)
480 0 0 480 1e0 static_mutex.o (ex /usr/lib/libboost_regex-mt.a)
1543 0 36 1579 62b cpp_regex_traits.o (ex /usr/lib/libboost_regex-mt.a)
3171 632 0 3803 edb regex_traits_defaults.o (ex /usr/lib/libboost_regex-mt.a)
5339 8 13 5360 14f0 c_regex_traits.o (ex /usr/lib/libboost_regex-mt.a)
5650 8 16 5674 162a wc_regex_traits.o (ex /usr/lib/libboost_regex-mt.a)
9075 4 32 9111 2397 regex.o (ex /usr/lib/libboost_regex-mt.a)
17052 8 4 17064 42a8 fileiter.o (ex /usr/lib/libboost_regex-mt.a)
61265 0 0 61265 ef51 wide_posix_api.o (ex /usr/lib/libboost_regex-mt.a)
61787 0 0 61787 f15b posix_api.o (ex /usr/lib/libboost_regex-mt.a)
80811 8 0 80819 13bb3 icu.o (ex /usr/lib/libboost_regex-mt.a)
116489 8 112 116609 1c781 instances.o (ex /usr/lib/libboost_regex-mt.a)
117874 8 112 117994 1ccea winstances.o (ex /usr/lib/libboost_regex-mt.a)
131104 0 0 131104 20020 cregex.o (ex /usr/lib/libboost_regex-mt.a)
612075 684 325 613084 95adc (TOTALS)
您可以得到高达60万〜仅从Boost.Regex未来如果某些或所有这些目标文件的获取链接到您的二进制文件。
You could get up to ~600K coming from Boost.Regex alone if some or all of those object files get linked into your binary.
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