新增]外部C＆QUOT;作为一个符号编译器选项？ [英] add "extern C" as a compiler option for a symbol?

问题描述

我和FIPS有能力OpenSSL的工作。源$ C ​​$ c为隔离的，不能改变。

要链接到OpenSSL库的静态版本，我们需要做的是：

 出口FIPS_SIG =`发现在/ usr /本地/ SSL -iname incore`
出口CC =`发现在/ usr /本地/ SSL -iname fipsld`
出口FIPSLS_CC =`找到的/ usr / bin中-iname gcc`
 

然后，只需执行：

  $ CC $ CFLAGS＆LT;来源和GT; -o myprogram＆LT;的OpenSSL库＆GT;
 

对于回转的原因是OpenSSL的将插入一个额外的源文件 - fips_ premain.c - 以及与节目源编译。 （会出现一些额外的步骤，但汇编 fips_ premain.c 是相关步骤）。

然而，当使用 G ++ ，一对夫妇的符号是不确定的，因为他们同当安装OpenSSL的C编译器编译，当如上调用G ++找不到他们

  /tmp/fips_$p$pmain-20db15.o：在功能`FINGERPRINT_ $ P $段Pmain（）：
/usr/local/ssl/fips-2.0/lib/fips_$p$pmain.c:103：未定义参考`FIPS_text_start（）
/usr/local/ssl/fips-2.0/lib/fips_$p$pmain.c:116：未定义参考`FIPS_incore_fingerprint（无符号字符*，无符号整型）
 

如果我添加了 - 不还原函数链接选项，这里是输出：

  /tmp/fips_$p$pmain-be4611.o：在功能`_Z19FINGERPRINT_ premainv：
/usr/local/ssl/fips-2.0/lib/fips_$p$pmain.c:103：未定义参考`_Z15FIPS_text_startv
/usr/local/ssl/fips-2.0/lib/fips_$p$pmain.c:116：未定义参考`_Z23FIPS_incore_fingerprintPhj
 

下面感兴趣的行 fips_ premain.c （约85行）：

 的extern常量无效* FIPS_text_start（），* FIPS_text_end（）;
的extern const的无符号字符FIPS_rodata_start []，FIPS_rodata_end [];
的extern unsigned char型FIPS_signature [20];
的extern unsigned int类型FIPS_incore_fingerprint（无符号字符*，无符号整型）;
 

有没有一种方法来标记符号为的externC命令行？

解决方案

与 G ++ 直供 -xc 开关编译命令行上的文件之前，会迫使它被编译为C文件，而不是默认的C ++。

从 Fipsld和C ++ 页：

  

打开fipsld ++并找到fips_ premain.c编译发生。它是通过变量{preMAIN_C}编译...结果
  结果
  更改行，以便-xçpreceeds$ {preMAIN_C}，而-x没有跟随它。

  $ {CC} $ {CANISTER_O_CMD：+$ {} CANISTER_O_CMD} \\
    -x C$ {preMAIN_C}-x无\\
    $ {_ WL_ $ P $}段Pmain$ @
 

  

在fips_ premain.c强制C语言编译适用于所有配置（库，共享对象和可执行文件），所以你是安全的将其应用到fipsld ++的所有部分。

I'm working with FIPS Capable OpenSSL. The source code is sequestered and cannot be changed.

To link to the static version of the OpenSSL library, all we need to do is:

export FIPS_SIG=`find /usr/local/ssl -iname incore`
export CC=`find /usr/local/ssl -iname fipsld`
export FIPSLS_CC=`find /usr/bin -iname gcc`

Then, simply perform:

$CC $CFLAGS <sources> -o myprogram <openssl libs>

The reasons for the gyration is OpenSSL will insert an additional source file - fips_premain.c - and compile it with the program sources. (Some additional steps occur, but the compilation of fips_premain.c is the relevant step).

However, when using g++, a couple of symbols are undefined because they were compiled with the C compiler when OpenSSL was installed, and g++ cannot find them when invoked as above:

/tmp/fips_premain-20db15.o: In function `FINGERPRINT_premain()':
/usr/local/ssl/fips-2.0/lib/fips_premain.c:103: undefined reference to `FIPS_text_start()'
/usr/local/ssl/fips-2.0/lib/fips_premain.c:116: undefined reference to `FIPS_incore_fingerprint(unsigned char*, unsigned int)'

If I add the --no-demangle linker option, here's what is output:

/tmp/fips_premain-be4611.o: In function `_Z19FINGERPRINT_premainv':
/usr/local/ssl/fips-2.0/lib/fips_premain.c:103: undefined reference to `_Z15FIPS_text_startv'
/usr/local/ssl/fips-2.0/lib/fips_premain.c:116: undefined reference to `_Z23FIPS_incore_fingerprintPhj'

Here are the lines of interest in fips_premain.c (around line 85):

extern const void         *FIPS_text_start(),  *FIPS_text_end();
extern const unsigned char FIPS_rodata_start[], FIPS_rodata_end[];
extern unsigned char       FIPS_signature[20];
extern unsigned int        FIPS_incore_fingerprint(unsigned char *,unsigned int);

Is there a way to mark a symbol as extern "C" from the command line?

解决方案

Supplying the -x c switch with g++ before the file on the compilation command line will force it to be compiled as a C file instead of the default C++.

From the Fipsld and C++ page:

Open fipsld++ and find occurrences where fips_premain.c is compiled. It is compiled through the variable {PREMAIN_C} ...

Change the lines so that -x c preceeds "${PREMAIN_C}", and -x none follows it.

${CC}  ${CANISTER_O_CMD:+"${CANISTER_O_CMD}"} \
    -x c "${PREMAIN_C}" -x none \
    ${_WL_PREMAIN} "$@"

Forcing C compilation on fips_premain.c applies to all configurations (libraries, shared objects, and executables), so you are safe to apply it to all sections of fipsld++.

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