From ae075e75f08482903be0bdb0cd2b812a6aaf46db Mon Sep 17 00:00:00 2001
From: Max Brunsfeld <maxbrunsfeld@gmail.com>
Date: Mon, 23 Mar 2020 14:29:29 -0700
Subject: [PATCH] tags: Avoid returning garbage pointer when length is zero

---
 tags/include/tree_sitter/tags.h |  4 ++--
 tags/src/c_lib.rs               | 16 +++++++++++++---
 2 files changed, 15 insertions(+), 5 deletions(-)

diff --git a/tags/include/tree_sitter/tags.h b/tags/include/tree_sitter/tags.h
index 6054edc4..946dc6f1 100644
--- a/tags/include/tree_sitter/tags.h
+++ b/tags/include/tree_sitter/tags.h
@@ -36,8 +36,8 @@ typedef struct {
   uint32_t line_end_byte;
   TSPoint start_point;
   TSPoint end_point;
-  const char *docs;
-  uint32_t docs_length;
+  uint32_t docs_start_byte;
+  uint32_t docs_end_byte;
 } TSTag;
 
 typedef struct TSTagger TSTagger;
diff --git a/tags/src/c_lib.rs b/tags/src/c_lib.rs
index a4e54151..0d61fb46 100644
--- a/tags/src/c_lib.rs
+++ b/tags/src/c_lib.rs
@@ -2,7 +2,7 @@ use super::{Error, TagKind, TagsConfiguration, TagsContext};
 use std::collections::HashMap;
 use std::ffi::CStr;
 use std::process::abort;
-use std::{fmt, slice, str};
+use std::{fmt, ptr, slice, str};
 use tree_sitter::Language;
 
 #[repr(C)]
@@ -92,6 +92,7 @@ pub extern "C" fn ts_tagger_add_language(
         Ok(e) => e,
         Err(_) => return TSTagsError::InvalidUtf8,
     };
+
     match TagsConfiguration::new(language, tags_query, locals_query) {
         Ok(c) => {
             tagger.languages.insert(scope_name.to_string(), c);
@@ -114,6 +115,7 @@ pub extern "C" fn ts_tagger_tag(
     let tagger = unwrap_mut_ptr(this);
     let buffer = unwrap_mut_ptr(output);
     let scope_name = unsafe { unwrap(CStr::from_ptr(scope_name).to_str()) };
+
     if let Some(config) = tagger.languages.get(scope_name) {
         buffer.tags.clear();
         buffer.docs.clear();
@@ -174,7 +176,11 @@ pub extern "C" fn ts_tags_buffer_delete(this: *mut TSTagsBuffer) {
 #[no_mangle]
 pub extern "C" fn ts_tags_buffer_tags(this: *const TSTagsBuffer) -> *const TSTag {
     let buffer = unwrap_ptr(this);
-    buffer.tags.as_ptr()
+    if buffer.tags.is_empty() {
+        ptr::null()
+    } else {
+        buffer.tags.as_ptr()
+    }
 }
 
 #[no_mangle]
@@ -186,7 +192,11 @@ pub extern "C" fn ts_tags_buffer_tags_len(this: *const TSTagsBuffer) -> u32 {
 #[no_mangle]
 pub extern "C" fn ts_tags_buffer_docs(this: *const TSTagsBuffer) -> *const i8 {
     let buffer = unwrap_ptr(this);
-    buffer.docs.as_ptr() as *const i8
+    if buffer.docs.is_empty() {
+        ptr::null()
+    } else {
+        buffer.docs.as_ptr() as *const i8
+    }
 }
 
 #[no_mangle]