Zend: Introduce inline helpers for raw C-string concatenation

Zend/zend_string.h

@@ -23,8 +23,14 @@
 #include "zend_gc.h"
 #include "zend_alloc.h"
 
+#include "zend_errors.h"
+
 BEGIN_EXTERN_C()
 
+ZEND_API ZEND_COLD ZEND_NORETURN void zend_error_noreturn(int type, const char *format, ...) ZEND_ATTRIBUTE_FORMAT(printf, 2, 3);
+
+#include "zend_multiply.h"
+
 typedef void (*zend_string_copy_storage_func_t)(void);
 typedef zend_string *(ZEND_FASTCALL *zend_new_interned_string_func_t)(zend_string *str);
 typedef zend_string *(ZEND_FASTCALL *zend_string_init_interned_func_t)(const char *str, size_t size, bool permanent);
@@ -316,6 +322,48 @@ static zend_always_inline zend_string *zend_string_safe_realloc(zend_string *s,
 	return ret;
 }
 
+static zend_always_inline char *zend_cstr_append_char(const char *str, size_t len, char c) {
+	char *res = (char *)safe_emalloc(len, 1, 2);
+	if (len > 0) {
+		memcpy(res, str, len);
+	}
+	res[len] = c;
+	res[len + 1] = '\0';
+	return res;
+}
+
+static zend_always_inline char *zend_cstr_concat(const char *s1, size_t len1, const char *s2, size_t len2) {
+	size_t size = zend_safe_address_guarded(1, len1, len2);
+	size = zend_safe_address_guarded(1, size, 1);
+	char *res = (char *)emalloc(size);
+	if (len1 > 0) {
+		memcpy(res, s1, len1);
+	}
+	if (len2 > 0) {
+		memcpy(res + len1, s2, len2);
+	}
+	res[len1 + len2] = '\0';
+	return res;
+}
+
+static zend_always_inline char *zend_cstr_concat3(const char *s1, size_t len1, const char *s2, size_t len2, const char *s3, size_t len3) {
+	size_t size = zend_safe_address_guarded(1, len1, len2);
+	size = zend_safe_address_guarded(1, size, len3);
+	size = zend_safe_address_guarded(1, size, 1);
+	char *res = (char *)emalloc(size);
+	if (len1 > 0) {
+		memcpy(res, s1, len1);
+	}
+	if (len2 > 0) {
+		memcpy(res + len1, s2, len2);
+	}
+	if (len3 > 0) {
+		memcpy(res + len1 + len2, s3, len3);
+	}
+	res[len1 + len2 + len3] = '\0';
+	return res;
+}
+
 static zend_always_inline void zend_string_free(zend_string *s)
 {
 	if (!ZSTR_IS_INTERNED(s)) {