From 959a80a46dbc4d3ad1bf8560dfacb585ccd8cac4 Mon Sep 17 00:00:00 2001
From: Jonathan Wakely <jwakely@redhat.com>
Date: Fri, 13 Dec 2024 10:54:29 +0000
Subject: [PATCH] libstdc++: Fix uninitialized data in
std::basic_spanbuf::seekoff
I noticed a -Wmaybe-uninitialized warning for this function, which turns
out to be correct. If the caller passes a valid std::ios_base::seekdir
value then there's no problem, but if they pass std::seekdir(999) then
we don't initialize the __base variable before adding it to __off.
Rather than initialize it to an arbitrary value, we should return an
error.
Also add [[unlikely]] attributes to the paths that return an error.
libstdc++-v3/ChangeLog:
* include/std/spanstream (basic_spanbuf::seekoff): Return an
error for invalid seekdir values.
---
libstdc++-v3/include/std/spanstream | 8 +++++---
1 file changed, 5 insertions(+), 3 deletions(-)
diff --git a/libstdc++-v3/include/std/spanstream b/libstdc++-v3/include/std/spanstream
index 98ad3fa856a7..23a340a746e8 100644
--- a/libstdc++-v3/include/std/spanstream
+++ b/libstdc++-v3/include/std/spanstream
@@ -168,7 +168,7 @@ template<typename _CharT, typename _Traits>
}
else
{
- off_type __base;
+ off_type __base{};
__which &= (ios_base::in|ios_base::out);
if (__which == ios_base::out)
@@ -182,11 +182,13 @@ template<typename _CharT, typename _Traits>
}
else if (__way == ios_base::end)
__base = _M_buf.size();
+ else /* way is not ios::beg, ios::cur, or ios::end */ [[unlikely]]
+ return __ret;
- if (__builtin_add_overflow(__base, __off, &__off))
+ if (__builtin_add_overflow(__base, __off, &__off)) [[unlikely]]
return __ret;
- if (__off < 0 || __off > _M_buf.size())
+ if (__off < 0 || __off > _M_buf.size()) [[unlikely]]
return __ret;
if (__which & ios_base::in)
--
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