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Reject C++ pointer casts to integer types that are too small [EDGcpfe/28892] - #454
In GNU C++ mode, including Clang mode, a cast of a pointer to an integer type too small to hold it was accepted with a warning. An example is (int)ptr on a 64-bit target. GCC 4.0 and later, and Clang, reject it.
In types.c, the gpp_mode test that allowed this is now gpp_version_is(<40000). GNU C++ before 4.0 accepted such casts with a warning, so code written for those versions keeps working. C and Microsoft mode are unchanged.
regressions/edg-28892 covers the error for object and function pointers, regressions/edg-28892-positive a cast to a wide enough type, and regressions/edg-28892-legacy the warning with --gnu_version=30406.
Nine imported Clang and GCC tests are re-recorded, and each now gets the error its source expects. gnu/cpp/parse/cast1 is an ILP32 test upstream, so it now fails on the 64-bit configurations, as it does with GCC, and passes on the 32-bit ones. gnu/cpp/template/sfinae13 now passes.
Tested with the full test suites for edg_x86_64 and edg_x86_64_cp, compared with a run of main, and with the new and changed tests for edg_x86_32 and edg_x86_32_cp.
The Changes entry uses this PR's number until there is an issue for it.
The conversion check no longer accepts undersized pointer-to-integer casts solely because GNU mode is enabled. Regression tests cover narrow object and function pointer casts, as well as a sufficiently wide destination type.
Changes: Pointer-to-integer cast validation
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Summary
Conversion rule and regression coverage src/types.c, tests/tests/regressions/edg-28892.sft.cpp, tests/tests/regressions/edg-28892-positive.sft.cpp, src/pending_changes/edg-28892-pointer-integer-cast.txt
GNU C++ mode no longer permits undersized destinations solely because GNU mode is enabled. C mode and Microsoft extensions retain the size exception. The regression tests check narrow object and function pointer casts and a sufficiently wide destination. The pending-change note records the restriction.
Add the expected recordings before relying on these regression tests to validate the pointer-cast change.
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The title "Reject C++ pointer casts to integer types that are too small [EDGcpfe/28892]" matches the main change. The raw summary shows that the pending-change note, the types.c update, and the new re…
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The title "Reject C++ pointer casts to integer types that are too small [EDGcpfe/28892]" matches the main change. The raw summary shows that the pending-change note, the types.c update, and the new regression tests all target pointer-to-integer reinterpret_cast conversions in C++ GNU mode when the destination is too small. The PR objectives describe the same change. The bracketed tracker tag is extra detail, but it does not make the title unclear.
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I tracked down why that gpp_mode is there. It's for this test case:
int main()
{
int *ptr;
int x;
x = (int)ptr;
x = (short)ptr; // warning in gcc 3.4.6
return 0;
}
Prior to GCC 4, this was accepted with a warning (https://godbolt.org/z/fG4YcKKr9).
Note that your test case was not accepted even then.
Rather than emulating this 100% accurately, I'd just replace the gpp_mode by gpp_version_is(<40000). That way any pre-GCC-4 code out there that relies on the leniency will continue to work (which should not be a whole lot), and modern code will track GCC 4+.
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Thanks for tracking that down. I replaced gpp_mode with gpp_version_is(<40000), so Clang mode and GNU C++ 4.0 and later now give the error. regressions/edg-28892-legacy is your example with --gnu_version=30406: (int)ptr and (short)ptr are accepted with a warning.
…/28892]
In GNU C++ mode (including Clang mode), a cast of a pointer to an integer
type too small to hold it was accepted with a warning. GCC 4.0 and
later, and Clang, reject it. Keep the leniency only when emulating GNU
C++ versions before 4.0, which accepted such casts with a warning.
Add regression tests for the error, the accepted wide cast, and the
pre-4.0 GNU behavior, and update the recordings of imported tests that
now get the error their sources expect. gnu/cpp/parse/cast1 is an ILP32
test upstream; it now fails on 64-bit configurations, as with GCC.
71iq
changed the title
Reject C++ pointer casts to undersized integers
Reject C++ pointer casts to integer types that are too small [EDGcpfe/28892]
Nov 8, 2026
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In GNU C++ mode, including Clang mode, a cast of a pointer to an integer type too small to hold it was accepted with a warning. An example is
(int)ptron a 64-bit target. GCC 4.0 and later, and Clang, reject it.In
types.c, thegpp_modetest that allowed this is nowgpp_version_is(<40000). GNU C++ before 4.0 accepted such casts with a warning, so code written for those versions keeps working. C and Microsoft mode are unchanged.regressions/edg-28892covers the error for object and function pointers,regressions/edg-28892-positivea cast to a wide enough type, andregressions/edg-28892-legacythe warning with--gnu_version=30406.Nine imported Clang and GCC tests are re-recorded, and each now gets the error its source expects.
gnu/cpp/parse/cast1is an ILP32 test upstream, so it now fails on the 64-bit configurations, as it does with GCC, and passes on the 32-bit ones.gnu/cpp/template/sfinae13now passes.Tested with the full test suites for edg_x86_64 and edg_x86_64_cp, compared with a run of main, and with the new and changed tests for edg_x86_32 and edg_x86_32_cp.
The
Changesentry uses this PR's number until there is an issue for it.Reported in discussion #298.