[clang] [hmaptool] Fix for empty prefixes and suffixes (PR #102571)

[via cfe-commits]

llvmbot wrote:


<!--LLVM PR SUMMARY COMMENT-->

@llvm/pr-subscribers-clang

Author: Shoaib Meenai (smeenai)

<details>
<summary>Changes</summary>

The previous logic could fail in some edge cases.


---
Full diff: https://github.com/llvm/llvm-project/pull/102571.diff


1 Files Affected:

- (modified) clang/utils/hmaptool/hmaptool (+5-2) 


``````````diff
diff --git a/clang/utils/hmaptool/hmaptool b/clang/utils/hmaptool/hmaptool
index d7754632b162b..aa400e3dd64e9 100755
--- a/clang/utils/hmaptool/hmaptool
+++ b/clang/utils/hmaptool/hmaptool
@@ -192,8 +192,11 @@ def action_write(name, args):
 
         key_idx = len(strtable)
         strtable += key + '\0'
-        prefix = os.path.dirname(value) + '/'
-        suffix = os.path.basename(value)
+        prefix, suffix = os.path.split(value)
+        # This guarantees that prefix + suffix == value in all cases, including when
+        # prefix is empty or contains a trailing slash or suffix is empty (hence the use
+        # of `len(value) - len(suffix)` instead of just `-len(suffix)`.
+        prefix += value[len(prefix) : len(value) - len(suffix)]
         prefix_idx = len(strtable)
         strtable += prefix + '\0'
         suffix_idx = len(strtable)

``````````

</details>


https://github.com/llvm/llvm-project/pull/102571