On 2026-07-20 15:18, Richard Earnshaw (foss) wrote:
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.
I ended up with `return 0;`. Note, I also changed `read_mem (NULL);` to
`read_mem (0);` to get rid of the include.
OK with one or other of those changes.
Pushed as r17-2559-g2e26607f7f14bd, r16-9314-g307954e9c03aba and
r15-11398-gcf69dd0145e174.
Kind regards,
Torbjörn
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"]
+}
