C语言 C 警告：声明无效
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C Warning: Statement with no effect
提问by aytee17
When trying to compile my prgram with:
尝试使用以下命令编译我的程序时：
gcc -pedantic -Wall -ansi
I get the warning: warning: statement with no effect
我收到警告：警告：声明无效
Referring to this line:
参考这一行：
for(currentDirection; currentDirection <= endDirection; currentDirection++)
Can anyone help me with this?
谁能帮我这个？
回答by ThiefMaster
currentDirection;does nothing.
currentDirection;什么也没做。
Replace your line with
将您的线路替换为
for(; currentDirection <= endDirection; currentDirection++)
Or, in case you just forgot to initialize the variable:
或者，如果您只是忘记初始化变量：
for(currentDirection = 0; currentDirection <= endDirection; currentDirection++)
回答by Mahesh
for(currentDirection; currentDirection <= endDirection; currentDirection++)
// ^^^^^^^^^^^^^^^ Its saying about the above statement.
First statement should have an assignment, which is not happening in this case and is the reason for the warning. Make sure currentDirectionis assigned to a valid value or it might have garbage and might later cause issues.
第一个语句应该有一个赋值，这在这种情况下不会发生，并且是警告的原因。确保currentDirection分配给一个有效的值，否则它可能有垃圾，以后可能会导致问题。
It is similar to when said -
这类似于说 -
int i = 10 ;
i ; // This statement is valid but has no effect.
回答by Cody Syring
In my experience this issue comes up when you do somthing along the lines of
根据我的经验，当您按照以下方式执行某些操作时会出现此问题
int x = 0;
for(x = 0;x < num; x++){}
When you are declaring your loop and you already initialize your variable, x you don't need to declare it a second time. So either do:
当您声明循环并且已经初始化变量 x 时，您不需要再次声明它。所以要么做：
int x = 0;
for(; x < num; x++){}
Or
或者
int x;
for(x = 0; x < num; x++){}
