C语言 assert() 带消息
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assert() with message
提问by Alexandru
I saw somewhere assert used with a message in the following way:
我看到某处断言以以下方式与消息一起使用：
assert(("message", condition));
This seems to work great, except that gcc throws the following warning:
这似乎很好用，除了 gcc 抛出以下警告：
warning: left-hand operand of comma expression has no effect
How can I stop the warning?
我怎样才能停止警告？
回答by pmg
Use -Wno-unused-valueto stop the warning; (the option -Wallincludes -Wunused-value).
使用-Wno-unused-value停止警告; （选项-Wall包括-Wunused-value）。
I think even better is to use another method, like
我认为更好的是使用另一种方法，例如
assert(condition && "message");
回答by bugfeeder
Try:
尝试：
#define assert__(x) for ( ; !(x) ; assert(x) )
use as such:
像这样使用：
assert__(x) {
printf("assertion will fail\n");
}
Will execute the block only when assert fails.
只有当断言失败时才会执行块。
IMPORTANT NOTE:This method will evaluate expression
xtwice, in casexevaluates tofalse! (First time, when theforloop is checking its condition; second time, when theassertis evaluating the passed expression!)
重要说明：此方法将对表达式求值
x两次，以防x求值为false! （第一次，当for循环检查其条件时；第二次，当assert评估传递的表达式时！）
回答by frmdstryr
If you want to pass a formatted message, you could use the following macros:
如果要传递格式化消息，可以使用以下宏：
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <assert.h>
#define clean_errno() (errno == 0 ? "None" : strerror(errno))
#define log_error(M, ...) fprintf(stderr, "[ERROR] (%s:%d: errno: %s) " M "\n", __FILE__, __LINE__, clean_errno(), ##__VA_ARGS__)
#define assertf(A, M, ...) if(!(A)) {log_error(M, ##__VA_ARGS__); assert(A); }
Then use it like printf:
然后像printf一样使用它：
// With no args
assertf(self != NULL,"[Server] Failed to create server.");
// With formatting args
assertf((self->socket = u_open(self->port)) != -1,"[Server] Failed to bind to port %i:",self->port);
// etc...
Output:
输出：
[ERROR] (../src/webserver.c:180: errno: Address already in use) [Server] Failed to bind to port 8080: webserver: ../src/webserver.c:180: server_run: Assertion `(self->socket = u_open(self->port)) != -1' failed.
[ERROR] (../src/webserver.c:180: errno: Address already in use) [Server] 无法绑定到端口 8080: webserver: ../src/webserver.c:180: server_run: Assertion `( self->socket = u_open(self->port)) != -1' 失败。
回答by Cacahuete Frito
You could write your own macro that provides the same usage of _Static_assert(expr, msg):
您可以编写自己的宏来提供相同的用法_Static_assert(expr, msg)：
#include <assert.h>
#include <stdbool.h>
#include <stdio.h>
/*
* void assert_msg(bool expr, const char *msg);
*/
#if !defined(NDEBUG)
#define assert_msg(expr, msg) do \
{ \
const bool e_ = expr; \
\
if (!e_) { \
fputs(msg, stderr); \
fputc('\n', stderr); \
assert(e_); \
} \
} while (0)
#else
#define assert_msg(expr, msg) do \
{ \
\
if (!(expr)) \
warn_bug(msg); \
} while (0)
#endif
I also have a macro warn_bug()that prints the name of the program, the file, the line, the function, the errno value and string, and a user message, even if asserts are disabled. The reason behind it is that it won't break the program, but it will warn that a bug will probably be present. You could just define assert_msgto be empty if defined(NDEBUG), though.
我还有一个宏warn_bug()，即使断言被禁用，它也会打印程序的名称、文件、行、函数、errno 值和字符串以及用户消息。其背后的原因是它不会破坏程序，但会警告可能存在错误。但是，您可以assert_msg将 if定义为空defined(NDEBUG)。
回答by Arthur2e5
By tradition, (void)communicates to the compiler that you are knowingly ignoring an expression:
按照传统，(void)向编译器传达您有意忽略表达式：
/* picard.c, TNG S6E11. */
#define assertmsg(x, msg) assert(((void) msg, x))
assertmsg(2+2==5, "There! are! four! lights!");
回答by JiaHao Xu
A function that takes const char*and returns truewould probably save you from all sorts of warnings:
一个接受const char*和返回的函数true可能会让你免于各种警告：
#include <assert.h>
int always_true(const char *msg) {
return 1;
}
#define assert_msg(expr, msg) assert((expr) && always_true(msg))
回答by Dhiraj
According to following link http://www.cplusplus.com/reference/clibrary/cassert/assert/
根据以下链接 http://www.cplusplus.com/reference/clibrary/cassert/assert/
assert is expecting only expression. May be you are using some overloaded function.
assert 只期待表达。可能是您正在使用某些重载函数。
According to this, only expression is allowed and thus you are getting this warning.
据此，只允许表达，因此您会收到此警告。
