C++: error: invalid conversion from 'const char*' to 'char*' [-fpermissive]

Meaning

In C++ a string literal has type const char[N], so char* s = "hi"; is ill-formed. The same rule applies to void* (needs a cast in C++) and to int to enum conversions. The fix is to make the target type const-correct, not to add -fpermissive.

Common causes

• String literal assigned to char* instead of const char*
• void* from malloc assigned without a cast (valid in C, not C++)
• const object passed where a non-const pointer is required
• Integer assigned to an enum or pointer type
• C code compiled as C++

Detailed fix by platform

Code examples

// error: invalid conversion from 'const char*' to 'char*'
// char* title = "Report";

const char* title = "Report";          // OK: read-only literal
std::string editable = "Report";       // OK: owns a copy

void* raw = std::malloc(16);
int* p = static_cast<int*>(raw);       // C++ needs the cast

How to diagnose

1. Source — Is the right-hand side a literal or a const object?
2. Target — Can the variable type be made const?
3. Language — Was this file meant to be compiled as C?

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