Resolved the problem of the iso c++ forbids converting a string constant to ‘char*’

Question

I am working on cpp, but I found the following warning message:

ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]

Is there any way to stabilize the issue “iso c++ forbids converting a string constant to ‘char*’”? I read a lot of topics about this, but all of them were trying to install anything. Is this the correct way, or any recommendation for me? Please find the beginning command below:

char const *q = "pin";
 char const *r = "\n\r";
 {
 while(client.findUntil(*q, *r))

while(client.findUntil("pin", "\n\r"))

hdtutoria · Accepted Answer

The cause: The warning shown that your program is ill-formed. You didn't provide the declaration, but we can assume from the context that the findUntil argument is char*. A string literal cannot be passed to such a function. The solution: You can fix this error by copying string literals into editable arrays:

char q[] = "pin";
char r[] = "

";
{
    while(client.findUntil(q, r))

Another option is to fix findUntil to accept a pointer to const char instead. Then, because string literals can be transformed to a pointer to const char, you can utilize them.

Adam Guillon · Answer

ISO C++ forbids converting a string constant to 'char*' [-Wwrite-strings]
while(client.findUntil("pin", "

"))

This warning indicates that your program is not well-formed. Although you didn't display the declaration, context can help us to determine that findUntil's argument is char*. A string literal may not be passed to such a function.

It was once well-formed, but now deprecated. To pass a string literal such as char* before C++11, it used to work.

I tried:

char const *q = "pin";
char const *r = "

";

These statements are true by themselves.

while(client.findUntil(*q, *r))

This is absurd. You were trying to pass a string previously, but you now indirect through the character pointeder so that you are passing a character. This cannot work unless the function is a template.

findUntil(q, r) will not work, either because pointers to const won’t implicitly transform to non-const.

The best solution is to convert string literals into modifiable ranges.

char q[] = "pin";
char r[] = "

";
{
 while(client.findUntil(q, r))

Another option is to change findUntil so that it accepts a pointer-to const char instead. String literals can then be used, as they can be converted into a pointer-to const char.

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Resolved the problem of the iso c++ forbids converting a string constant to ‘char*’