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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.
GNU C++ and Clang modes now report an error when a pointer is cast to an integer type too small to hold it, instead of accepting the cast with a warning.
GNU C++ versions before 4.0 retain the legacy behavior of accepting these casts with a warning.
No actionable comments were generated in the recent review.
Walkthrough
The conversion check no longer accepts undersized pointer-to-integer casts solely because GNU mode is enabled. The exception remains for C mode, Microsoft extensions, and emulated GNU C++ versions before 4.0. Regression tests and expected diagnostic outputs cover these rules.
Changes: Pointer-to-integer cast validation
Layer / File(s)
Summary
Conversion rule and change note src/types.c, src/pending_changes/edg-28892-pointer-integer-cast.txt
The conversion check limits the undersized-destination exception to C mode, Microsoft extensions, and emulated GNU C++ versions before 4.0. The pending-change note describes the diagnostic change and exception.
Regression cases for cast widths and GNU versions tests/tests/regressions/edg-28892*.sft.cpp, tests/tests/regressions/.edg-28892*.rto/*
Regression cases cover narrow object and function pointer casts, a sufficiently wide destination, and GNU C++ 3.4.6 casts. Expected outputs record errors for narrow casts and warnings for the legacy casts.
Expected Clang and GNU outputs replace pointer-to-smaller-integer warnings with invalid-type-conversion errors. The GNU template output fixtures for the cast checks are removed.
This change makes GNU C++ mode, including Clang mode, reject casts of pointers to integer types too small to hold them. GNU C++ before 4.0 keeps the old warning. Regression tests and updated diagnostic baselines cover the new behavior. No merge-blocking risk remains.
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The title states the main change: C++ pointer casts to integer types too small to hold the pointer are now rejected. The raw summary confirms this change in src/types.c, the pending-change note, and t…
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The title states the main change: C++ pointer casts to integer types too small to hold the pointer are now rejected. The raw summary confirms this change in src/types.c, the pending-change note, and the regression tests. The PR objectives describe the same change for GNU C++ 4.0 and later, including Clang mode, with the pre-4.0 warning behavior retained. The bracketed issue tag is a minor addition and does not affect relevance.
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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.
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