gcc警告

川长思鸟来 2022-08-07 01:32 213阅读 0赞

# 各个层次的gcc警告 #

从上到下覆盖

## 变量(代码)级:指定某个变量警告 ##

int a __attribute__ ((unused));

指定该变量为"未使用的".即使这个变量没有被使用,编译时也会忽略则个警告输出.

## 文件级:在源代码文件中诊断(忽略/警告) ##

语法:

#pragma GCC diagnostic [error|warning|ignored] "-W<警告选项>"

诊断-忽略:(关闭警告)

#pragma  GCC diagnostic ignored  "-Wunused"
    #pragma  GCC diagnostic ignored  "-Wunused-parameter"

诊断-警告:(开启警告)

#pragma  GCC diagnostic warning  "-Wunused"
    #pragma  GCC diagnostic warning  "-Wunused-parameter"

诊断-错误:(开启警告-升级为错误)

#pragma  GCC diagnostic error  "-Wunused"
    #pragma  GCC diagnostic error  "-Wunused-parameter"

用法:

在文件开头处关闭警告,在文件结尾出再开启警告,这样可以忽略该文件中的指定警告.

## 项目级:命令行/编译参数指定 ##

警告:  
gcc main.c -Wall 忽略:  
gcc mian.c -Wall -Wno-unused-parameter //开去`all`警告,但是忽略 `-unused-parameter`警告

选项格式: `-W[no-]<警告选项>`  
如 : `-Wno-unused-parameter # no- 表示诊断时忽略这个警告`

`原文：https://github.com/zodiac1111/note/blob/master/note/gcc/gcc-ignored-warning.markdown#%E6%96%87%E4%BB%B6%E7%BA%A7%E5%9C%A8%E6%BA%90%E4%BB%A3%E7%A0%81%E6%96%87%E4%BB%B6%E4%B8%AD%E8%AF%8A%E6%96%AD%E5%BF%BD%E7%95%A5%E8%AD%A6%E5%91%8A`

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#### 6.60.10 Diagnostic Pragmas ####

GCC allows the user to selectively enable or disable certain types of diagnostics, and change the kind of the diagnostic. For example, a project's policy might require that all sources compile with \-Werror but certain files might have exceptions allowing specific types of warnings. Or, a project might selectively enable diagnostics and treat them as errors depending on which preprocessor macros are defined.

`#pragma GCC diagnostic` kind option

Modifies the disposition of a diagnostic. Note that not all diagnostics are modifiable; at the moment only warnings (normally controlled by ‘ \-W...’) can be controlled, and not all of them. Use \-fdiagnostics-show-option to determine which diagnostics are controllable and which option controls them.

kind is ‘error’ to treat this diagnostic as an error, ‘warning’ to treat it like a warning (even if \-Werror is in effect), or ‘ignored’ if the diagnostic is to be ignored. option is a double quoted string that matches the command-line option.

#pragma GCC diagnostic warning "-Wformat"
              #pragma GCC diagnostic error "-Wformat"
              #pragma GCC diagnostic ignored "-Wformat"

Note that these pragmas override any command-line options. GCC keeps track of the location of each pragma, and issues diagnostics according to the state as of that point in the source file. Thus, pragmas occurring after a line do not affect diagnostics caused by that line.

`#pragma GCC diagnostic push` `#pragma GCC diagnostic pop`

Causes GCC to remember the state of the diagnostics as of each `push`, and restore to that point at each `pop`. If a `pop` has no matching `push`, the command-line options are restored.

#pragma GCC diagnostic error "-Wuninitialized"
                foo(a);                       /* error is given for this one */
              #pragma GCC diagnostic push
              #pragma GCC diagnostic ignored "-Wuninitialized"
                foo(b);                       /* no diagnostic for this one */
              #pragma GCC diagnostic pop
                foo(c);                       /* error is given for this one */
              #pragma GCC diagnostic pop
                foo(d);                       /* depends on command-line options */

GCC also offers a simple mechanism for printing messages during compilation.

`#pragma message` string

Prints string as a compiler message on compilation. The message is informational only, and is neither a compilation warning nor an error.

#pragma message "Compiling " __FILE__ "..."

string may be parenthesized, and is printed with location information. For example,

#define DO_PRAGMA(x) _Pragma (#x)
              #define TODO(x) DO_PRAGMA(message ("TODO - " #x))
              
              TODO(Remember to fix this)

prints ‘/tmp/file.c:4: note: \#pragma message: TODO - Remember to fix this’.

原文： [https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Pragmas.html][https_gcc.gnu.org_onlinedocs_gcc_Diagnostic-Pragmas.html]

[https_gcc.gnu.org_onlinedocs_gcc_Diagnostic-Pragmas.html]: https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Pragmas.html