LibC: Deprecate strcpy(), strncpy(), strcat() and strncat() :^)

And also mark strlcpy() and strlcat() with __attribute__((warn_unused_result)).

Since our code is warning-free, this ensures we never misuse those functions.
(Or are very sure about doing it when turning off the warning for a particular
piece of code.)

Libraries/LibC/string.h

@@ -33,27 +33,40 @@ __BEGIN_DECLS
 
 size_t strlen(const char*);
 size_t strnlen(const char*, size_t maxlen);
+
 int strcmp(const char*, const char*);
 int strncmp(const char*, const char*, size_t);
+int strcasecmp(const char*, const char*);
+int strncasecmp(const char*, const char*, size_t);
+
 int memcmp(const void*, const void*, size_t);
 void* memcpy(void*, const void*, size_t);
 void* memmove(void*, const void*, size_t);
 void* memchr(const void*, int c, size_t);
 const void* memmem(const void* haystack, size_t, const void* needle, size_t);
+
 void bzero(void*, size_t);
 void bcopy(const void*, void*, size_t);
 void* memset(void*, int, size_t);
+
 __attribute__((malloc)) char* strdup(const char*);
 __attribute__((malloc)) char* strndup(const char*, size_t);
+
+__attribute__((deprecated("use strlcpy or String::copy_characters_to_buffer")))
 char* strcpy(char* dest, const char* src);
-size_t strlcpy(char* dest, const char* src, size_t);
+__attribute__((deprecated("use strlcpy or String::copy_characters_to_buffer")))
 char* strncpy(char* dest, const char* src, size_t);
+__attribute__((warn_unused_result)) size_t strlcpy(char* dest, const char* src, size_t);
+
 char* strchr(const char*, int c);
 char* strchrnul(const char*, int c);
 char* strstr(const char* haystack, const char* needle);
 char* strrchr(const char*, int c);
-char* strcat(char* dest, const char* src);
-char* strncat(char* dest, const char* src, size_t);
+
+__attribute__((deprecated("use strlcat"))) char* strcat(char* dest, const char* src);
+__attribute__((deprecated("use strlcat"))) char* strncat(char* dest, const char* src, size_t);
+__attribute__((warn_unused_result)) size_t strlcat(char* dest, const char* src, size_t);
+
 size_t strspn(const char*, const char* accept);
 size_t strcspn(const char*, const char* reject);
 char* strerror(int errnum);

Libraries/LibC/termcap.cpp

@@ -95,6 +95,11 @@ static void ensure_caps()
     caps->set("li", "25");
 }
 
+// Unfortunately, tgetstr() doesn't accept a size argument for the buffer
+// pointed to by area, so we have to use bare strcpy().
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+
 char* tgetstr(const char* id, char** area)
 {
     ensure_caps();
@@ -113,6 +118,8 @@ char* tgetstr(const char* id, char** area)
     return nullptr;
 }
 
+#pragma GCC diagnostic pop
+
 int tgetflag(const char* id)
 {
     (void)id;

Userland/Tests/Kernel/elf-symbolication-kernel-read-exploit.cpp

@@ -37,6 +37,8 @@ asm("haxcode:\n"
 extern "C" void haxcode();
 extern "C" void haxcode_end();
 
+#pragma GCC diagnostic ignored "-Wdeprecated-declarations"
+
 int main()
 {
     char buffer[16384];