https://gcc.gnu.org/g:bf06ae0fe3309e0835cbb5b21f91d7cb56126b70
commit r15-10962-gbf06ae0fe3309e0835cbb5b21f91d7cb56126b70 Author: Tomasz Kamiński <[email protected]> Date: Fri Feb 27 19:55:19 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: New test. Reviewed-by: Jonathan Wakely <[email protected]> Signed-off-by: Tomasz Kamiński <[email protected]> (cherry picked from commits 8758503918a91dacff4dbc7126eced21787fbfc9 bfc2b87f8244a13ab00e8e3fe2af1d6d18fcaa36 a523d1ecc89dcb7ea205e3de22d00443d4a0d91d) Diff: --- libstdc++-v3/include/std/streambuf | 5 +++++ .../testsuite/24_iterators/istreambuf_iterator/105580.cc | 15 +++++++++++++++ 2 files changed, 20 insertions(+) diff --git a/libstdc++-v3/include/std/streambuf b/libstdc++-v3/include/std/streambuf index 0d0f7a826282..3b70af1ed063 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 new file mode 100644 index 000000000000..e1ef4b107396 --- /dev/null +++ b/libstdc++-v3/testsuite/24_iterators/istreambuf_iterator/105580.cc @@ -0,0 +1,15 @@ +// { dg-compile } +// { dg-additional-options "-Wnull-dereference" } + +#include <string> +#include <sstream> + +int main() +{ + std::istringstream in("Hello, world"); + std::istreambuf_iterator<char> it(in), end; + std::string ss(it, end); + return 0; +} + +// { dg-bogus "null pointer dereference" "" { target *-*-* } 0 }
