fix for -cstrict -cc clang-18 passes for markdown

Author: spytheman

src/html.v

@@ -19,6 +19,6 @@ fn write_data_cb(txt &char, size u32, mut sb strings.Builder) {
 
 pub fn to_html(input string) string {
 	mut wr := strings.new_builder(200)
-	C.md_html(input.str, input.len, write_data_cb, &wr, C.MD_DIALECT_GITHUB, 0)
+	C.md_html(voidptr(input.str), input.len, write_data_cb, &wr, C.MD_DIALECT_GITHUB, 0)
 	return wr.str().trim_space()
 }

src/html_experimental.v

@@ -64,7 +64,7 @@ fn tos_attribute(attr &C.MD_ATTRIBUTE, mut wr strings.Builder) {
 		typ := unsafe { MD_TEXTTYPE(attr.substr_types[i]) }
 		off := unsafe { attr.substr_offsets[i] }
 		size := unsafe { attr.substr_offsets[i + 1] - off }
-		text := unsafe { (attr.text + off).vstring_with_len(int(size)) }
+		text := unsafe { (&char(attr.text) + off).vstring_with_len(int(size)) }
 
 		match typ {
 			.md_text_null_char {

src/renderer.v

@@ -55,7 +55,7 @@ fn renderer_debug_log_cb(msg &char, mut renderer Renderer) {
 pub fn render(src string, mut renderer Renderer) !string {
 	parser := new(u32(C.MD_DIALECT_GITHUB), renderer_enter_block_cb, renderer_leave_block_cb,
 		renderer_enter_span_cb, renderer_leave_span_cb, renderer_text_cb, renderer_debug_log_cb)
-	err_code := parse(src.str, u32(src.len), &parser, &renderer)
+	err_code := parse(voidptr(src.str), u32(src.len), &parser, &renderer)
 	if err_code != 0 {
 		return error_with_code('Something went wrong while parsing.', err_code)
 	}

thirdparty/md4c/md4c.c

@@ -3129,6 +3129,7 @@ md_collect_marks(MD_CTX* ctx, const MD_LINE* lines, int n_lines, int table_mode)
                     /* Advance the current line accordingly. */
                     if(off > line_end) {
                         line = md_lookup_line(off, line, line_term - line);
+					    if(NULL == line) exit(15);
                         line_end = line->end;
                     }
                     continue;