https://gcc.gnu.org/g:bfc2b87f8244a13ab00e8e3fe2af1d6d18fcaa36
commit r16-7844-gbfc2b87f8244a13ab00e8e3fe2af1d6d18fcaa36 Author: Tomasz Kamiński <[email protected]> Date: Fri Feb 27 20:14:44 2026 +0100 libstdc++: Add #pragma to slience null-dereference warning in istreambuf_iterator::operator++ [PR105580] The warning was produced by following sequence, given an istream_iterator<char> it, such that *it will result in hitting EoF in it->_M_get(), and thus clearing _M_sbuf, the subsequent call to ++it, will result in _M_sbuf->sbumpc() call on null pointer. This is however an false-positive, as in such situation it == istream_iteator() returns true, and the iterator should not be incremented in first place. This patch sliences the issue, by disabling the "-Wnull-dereference" using GCC diagnostic pragmas. To work correctly the pragmas needs to be placed around streambuf functions on which the issue originating from istreambuf_iterator are reported. PR libstdc++/105580 libstdc++-v3/ChangeLog: * include/std/streambuf (streambuf::gptr, streambuf::egptr) (streambuf::gbump): Surround with pragma disabling -Wnull-dereference. * testsuite/24_iterators/istreambuf_iterator/105580.cc: Remove check for warning being emitted. Reviewed-by: Jonathan Wakely <[email protected]> Signed-off-by: Tomasz Kamiński <[email protected]> Diff: --- libstdc++-v3/include/std/streambuf | 5 +++++ libstdc++-v3/testsuite/24_iterators/istreambuf_iterator/105580.cc | 2 -- 2 files changed, 5 insertions(+), 2 deletions(-) diff --git a/libstdc++-v3/include/std/streambuf b/libstdc++-v3/include/std/streambuf index d6036bd5ddc4..f013aa06c28b 100644 --- a/libstdc++-v3/include/std/streambuf +++ b/libstdc++-v3/include/std/streambuf @@ -490,6 +490,10 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION char_type* eback() const { return _M_in_beg; } +// Required to silence false-positive warnings originating from istream_iterator::operator++, +// see PR105580. +#pragma GCC diagnostic push +#pragma GCC diagnostic ignored "-Wnull-dereference" char_type* gptr() const { return _M_in_cur; } @@ -505,6 +509,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION */ void gbump(int __n) { _M_in_cur += __n; } +#pragma GCC diagnostic pop /** * @brief Setting the three read area pointers. diff --git a/libstdc++-v3/testsuite/24_iterators/istreambuf_iterator/105580.cc b/libstdc++-v3/testsuite/24_iterators/istreambuf_iterator/105580.cc index 85f888b86e72..87edf999ffcd 100644 --- a/libstdc++-v3/testsuite/24_iterators/istreambuf_iterator/105580.cc +++ b/libstdc++-v3/testsuite/24_iterators/istreambuf_iterator/105580.cc @@ -1,5 +1,4 @@ // { dg-compile } -// { dg-require-normal-mode "" } // { dg-additional-options "-Wnull-dereference" } #include <string> @@ -12,5 +11,4 @@ int main() std::string ss(it, end); return 0; } -// { dg-warning ".*null pointer dereference" "" { target *-*-* } 0 }
