On 15/07/2026 06:04, Torbjörn SVENSSON wrote: > Hi Richard, > > I've updated to your sugestion, but used exit(0) instead of _exit(0) as > 'exit' is defined in the stdlib.h header file, while '_exit' is not. > If we use '_exit', we need to have a function prototype too. > Including stdlib.h, or stddef.h, is required for 'NULL' regardless. > > Ok for trunk, releases/gcc-16 and releases/gcc-15? >
Hmm, actually I think we should use __builtin_exit(), so we don't need to declare it. This saves a lot of header pre-processing when compiling the test as now we no-longer need stddef.h. Many tests call __builtin_abort() rather than abort() for the same reason. But equally, I suspect we could just return 0 from main and let the normal program termination code handle the exit code that way. Either way avoids the need to include stddef.h. OK with one or other of those changes. R. > Kind regards, > Torbjörn > -- > > As arm-none-eabi targets might have readable memory at address 0, > g++.dg/torture/pr101373.C test will "work" on some targets, while others > might tigger a fault. To avoid the ambiguity, lest skip the test if > target allows null to be dereferenced. > > PR testsuite/126261 > > gcc/ChangeLog: > > * doc/sourcebuild.texi (can_deref_null): Document. > > gcc/testsuite/ChangeLog: > > * g++.dg/torture/pr101373.C: Use effective-target can_deref_null. > * lib/target-supports.exp (check_effective_target_can_deref_null): > New proc. > > Signed-off-by: Torbjörn SVENSSON <[email protected]> > --- > gcc/doc/sourcebuild.texi | 4 ++++ > gcc/testsuite/g++.dg/torture/pr101373.C | 1 + > gcc/testsuite/lib/target-supports.exp | 21 +++++++++++++++++++++ > 3 files changed, 26 insertions(+) > > diff --git a/gcc/doc/sourcebuild.texi b/gcc/doc/sourcebuild.texi > index 0e08ef5e645..e2530cf159d 100644 > --- a/gcc/doc/sourcebuild.texi > +++ b/gcc/doc/sourcebuild.texi > @@ -2739,6 +2739,10 @@ Target supports the execution of @code{amx-movrs} > instructions. > @item amx_fp8 > Target supports the execution of @code{amx-fp8} instructions. > > +@item can_deref_null > +Target runtime permits dereferencing a null pointer without trapping, for > +example because address zero is mapped and readable. > + > @item cell_hw > Test system can execute AltiVec and Cell PPU instructions. > > diff --git a/gcc/testsuite/g++.dg/torture/pr101373.C > b/gcc/testsuite/g++.dg/torture/pr101373.C > index f8c809739e2..45f1e455eec 100644 > --- a/gcc/testsuite/g++.dg/torture/pr101373.C > +++ b/gcc/testsuite/g++.dg/torture/pr101373.C > @@ -1,5 +1,6 @@ > // { dg-do run } > // { dg-xfail-run-if "PR100409" { *-*-* } } > +// { dg-skip-if "PR126261" { can_deref_null } } > > int __attribute__((const,noipa)) foo (int j) > { > diff --git a/gcc/testsuite/lib/target-supports.exp > b/gcc/testsuite/lib/target-supports.exp > index edd1290bd9e..9e4966cff0f 100644 > --- a/gcc/testsuite/lib/target-supports.exp > +++ b/gcc/testsuite/lib/target-supports.exp > @@ -15134,3 +15134,24 @@ proc check_effective_target_memtag_exec {} { > } > return 1; > } > + > +# Return 1 if the target runtime can deref null, 0 otherwise. > +# Cache the result. > + > +proc check_effective_target_can_deref_null { } { > + return [check_runtime can_deref_null { > + #include <stdlib.h> > + char __attribute__((noipa)) > + read_mem (volatile char *p) > + { > + return *p; > + } > + > + int > + main () > + { > + read_mem (NULL); > + exit (0); > + } > + } "-O0 -fno-delete-null-pointer-checks -Wno-null-dereference"] > +}
