[libc++][regex] Fix #51028 throw exception in the case of wrong range

[insanustu]

Starting and ending parameters are considered to decide that a range is a correct one

Fix #51028

[github-actions]

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[llvmbot]

@llvm/pr-subscribers-libcxx

Author: Lazarev Alexei (insanustu)

Changes

Starting and ending parameters are considered to decide that a range is a correct one

---

Full diff: https://github.com/llvm/llvm-project/pull/148231.diff

2 Files Affected:

• (modified) libcxx/include/regex (+1-1)
• (modified) libcxx/test/std/re/re.regex/re.regex.construct/bad_range.pass.cpp (+1)

diff --git a/libcxx/include/regex b/libcxx/include/regex
index bbc21e244dd17..958168a88535d 100644
--- a/libcxx/include/regex
+++ b/libcxx/include/regex
@@ -2120,7 +2120,7 @@ public:
       __ranges_.push_back(
           std::make_pair(__traits_.transform(__b.begin(), __b.end()), __traits_.transform(__e.begin(), __e.end())));
     } else {
-      if (__b.size() != 1 || __e.size() != 1)
+      if (__b.size() != 1 || __e.size() != 1 || __b[0] > __e[0])
         std::__throw_regex_error<regex_constants::error_range>();
       if (__icase_) {
         __b[0] = __traits_.translate_nocase(__b[0]);
diff --git a/libcxx/test/std/re/re.regex/re.regex.construct/bad_range.pass.cpp b/libcxx/test/std/re/re.regex/re.regex.construct/bad_range.pass.cpp
index 023bc0ee79f44..f7ccf2d334022 100644
--- a/libcxx/test/std/re/re.regex/re.regex.construct/bad_range.pass.cpp
+++ b/libcxx/test/std/re/re.regex/re.regex.construct/bad_range.pass.cpp
@@ -33,6 +33,7 @@ int main(int, char**)
 {
     assert(error_range_thrown("([\\w-a])"));
     assert(error_range_thrown("([a-\\w])"));
+    assert(error_range_thrown("([w-a])"));
 
   return 0;
 }

[frederick-vs-ja]

Thanks! I edited the PR description to associate this PR with the issue to fix.

[github-actions]

✅ With the latest revision this PR passed the C/C++ code formatter.

[ldionne]

LGTM, thanks for the fix!

[ldionne]

Should we be using char_traits::lt to perform this comparison though?

[insanustu]

Done

[ldionne]

This can be merged once CI is green (whoever sees it first).