149 lines
4.6 KiB
Markdown
149 lines
4.6 KiB
Markdown
# GCC 编译连接参数
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## 1.编译参数
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### 1.1.编译警告控制参数
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#### 1.1.1.Werror
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-Werror：将所有的警告当成错误进行处理。
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#### 1.1.2.Wall
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-Wall：打开 gcc 的所有警告，主要包括以下部分：
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```blk
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-Waddress
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-Warray-bounds=1 (only with -O2)
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-Wbool-compare
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-Wbool-operation
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-Wc++11-compat-Wc++14-compat
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-Wcatch-value (C++ and Objective-C++ only)
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-Wchar-subscripts：警告如果数组下标有char类型。 这是错误的常见原因，因为程序员经常忘记这种类型是在某些机器上签名的。
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-Wcomment
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-Wduplicate-decl-specifier (C and Objective-C only)
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-Wenum-compare (in C/ObjC; this is on by default in C++)
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-Wformat
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-Wformat-security：开启类型不匹配警告。
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-Wint-in-bool-context
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-Wimplicit (C and Objective-C only)
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-Wimplicit-int (C and Objective-C only)
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-Wimplicit-function-declaration (C and Objective-C only)
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-Winit-self (only for C++)
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-Wlogical-not-parentheses
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-Wmain (only for C/ObjC and unless -ffreestanding)
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-Wmaybe-uninitialized
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-Wmemset-elt-size
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-Wmemset-transposed-args
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-Wmisleading-indentation (only for C/C++)
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-Wmissing-attributes
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-Wmissing-braces (only for C/ObjC)
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-Wmultistatement-macros
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-Wnarrowing (only for C++)
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-Wnonnull
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-Wnonnull-compare
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-Wopenmp-simd
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-Wparentheses
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-Wpointer-sign
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-Wreorder
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-Wrestrict
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-Wreturn-type
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-Wsequence-point
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-Wsizeof-pointer-div
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-Wsizeof-pointer-memaccess
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-Wstrict-aliasing
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-Wstrict-overflow=1
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-Wswitch
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-Wtautological-compare
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-Wtrigraphs
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-Wuninitialized
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-Wunknown-pragmas
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-Wunused-function：开启未使用的函数警告。
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-Wunused-label
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-Wunused-value
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-Wunused-variable
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-Wvolatile-register-var
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```
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每个警告参数都有对应的“-Wno-”参数实现相反的控制，例如：
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```blk
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-Wno-unused-parameter：关闭未使用的参数警告。
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-Wno-unused-function：关闭未使用的函数警告。
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-Wno-format-security：关闭类型不匹配警告。
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-Wno-sign-compare：关闭有符号数和无符号数比较警告。
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```
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在同时开启 -Wall 和 -Werror 时将使编译警告变为编译错误，此时语法检查非常严格，如需放开某些限制，可结合“-Wno-”类参数使用，例如：-Wall -Werror -Wno-unused-parameter -Wno-unused-function。
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#### 1.1.3.Wextra
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-Wextra：启用一些未由-Wall启用的额外警告标志。 （此选项过去称为-W ，旧名称仍然受支持，但更新的名称更具描述性。）
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```blk
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-Wclobbered
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-Wcast-function-type
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-Wempty-body
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-Wignored-qualifiers
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-Wimplicit-fallthrough=3
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-Wmissing-field-initializers
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-Wmissing-parameter-type (C only)
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-Wold-style-declaration (C only)
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-Woverride-init
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-Wsign-compare (C only)：开启有符号数和无符号数比较警告。
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-Wtype-limits
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-Wuninitialized
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-Wshift-negative-value (in C++03 and in C99 and newer)
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-Wunused-parameter (only with -Wunused or -Wall)：开启未使用的参数警告。
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-Wunused-but-set-parameter (only with -Wunused or -Wall)
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```
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选项 -Wextra 还会打印以下情况的警告消息：
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指针与整数零与< ， <= ， >或>= 。
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（仅限C ++）枚举器和非枚举器都出现在条件表达式中。
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（仅限C ++）不明确的虚拟基础。
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（仅限C ++）为已声明为register的数组下标。
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（仅限C ++）取得已声明register的变量的地址。
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（仅限C ++）基类不在派生类的复制构造函数中初始化。
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## 2.连接参数
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### 2.1.rpath/rpath-link
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如果 prog 依赖 libfoobar.so，而 libfoobar.so libfoo.so 和 libbar.so，按如下方式编译 program 将产生编译错误：
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```bash
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$ gcc -c -Wall main.c
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$ gcc -o prog main.o -L. -lfoobar
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/usr/bin/ld: warning: libfoo.so, needed by ./libfoobar.so, not found (try using -rpath or -rpath-link)
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/usr/bin/ld: warning: libbar.so, needed by ./libfoobar.so, not found (try using -rpath or -rpath-link)
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./libfoobar.so: undefined reference to `bar'
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./libfoobar.so: undefined reference to `foo'
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collect2: error: ld returned 1 exit status
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```
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此时可在编译 prog 时增加 -rpath/-rpath-link 参数：
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```bash
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gcc -o prog main.o -L. -lfoobar -Wl,-rpath=$(pwd)
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```
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即可。此时能够正常编译和运行 prog，因为相关信息已经被写入到 libfoobar.so 文件中：
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```bash
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$ readelf -d prog
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Dynamic section at offset 0xe08 contains 26 entries:
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Tag Type Name/Value
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0x0000000000000001 (NEEDED) Shared library: [libfoobar.so]
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0x0000000000000001 (NEEDED) Shared library: [libc.so.6]
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0x000000000000000f (RPATH) Library rpath: [/home/imk/develop/so/scrap]
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... ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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...
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```
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## 3.外部参考资料
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1. [gcc警告选项汇总](https://blog.csdn.net/qq_17308321/article/details/79979514)
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