Issue #22102 has been updated by nobu (Nobuyoshi Nakada). Expose `rb_str_to_cstr`? ---------------------------------------- Feature #22102: C API to obtain a C string from a Ruby String https://bugs.ruby-lang.org/issues/22102#change-117554 * Author: rhenium (Kazuki Yamaguchi) * Status: Open ---------------------------------------- Extracted from https://bugs.ruby-lang.org/issues/19315#note-35 It would be nice to have a utility function whose sole purpose is to obtain a C string (NUL-terminated and containing no NUL bytes) from a Ruby String. I suggest adding something like the following to the public C API: ```c /** * Returns a pointer to the string contents as a C string. This checks that the * string does not contain embedded NUL bytes and that it is properly * NUL-terminated. * * @param[in] str String in question. * @exception rb_eArgError String contents include a NUL byte in the middle. * @return Pointer to its contents. * @pre `str` must be an instance of ::RString. */ const char *rb_str_cstr(VALUE str); ``` While extensions can currently use `StringValueCStr(val)`, there are cases where it's inconvenient. - The argument `val` needs to be addressable and modifiable, even if a type conversion is not needed. ```c const char *ptr = StringValueCStr(rb_ary_entry(ary, 0)); // Won't compile ``` - Repeating `StringValue*()` calls on the same object to perform different checks is awkward. ```c // Let's say, `val_a` and `val_b` are passed as an input, and the types are unknown StringValueCStr(val_a); // The result is unusable because the next line can invalidate it const char *b = StringValueCStr(val_b); // `val_b.to_str` can mutate `val_a` const char *a = StringValueCStr(val_a); // So you have to check `val_a` again ``` -- https://bugs.ruby-lang.org/