Re: Still seeing Failed assertion: "p[i] == 0" on armv7 buildworld [gdb backtrace! End of area has 0x5a5a5a5a sequence]

[I got another little block of time again and have a little
more information.]

On Nov 18, 2025, at 10:39, Mark Millard <[email protected]> wrote:

> On Nov 18, 2025, at 10:18, Mark Millard <[email protected]> wrote:
> 
>> I modified system clang to not register its 2 SIGABRT handlers.
>> 
>> The backtrace has the jemalloc call stack activity as well.
>> 
>> (gdb) bt
>> #0  thr_kill () at thr_kill.S:4
>> #1  0x2a08ef24 in __raise (s=6) at /usr/src/lib/libc/gen/raise.c:48
>> #2  0x2a145f38 in abort () at /usr/src/lib/libc/stdlib/abort.c:61
>> #3  0x2a196128 in ehooks_debug_zero_check (addr=addr@entry=0x2b629000, size=size@entry=12288) at /usr/src/contrib/jemalloc/include/jemalloc/internal/ehooks.h:170
>> #4  0x2a191f60 in ehooks_alloc (tsdn=0x2a2e4060, ehooks=0x2a600080, new_addr=0x0, size=<optimized out>, alignment=4096, zero=0xffff6f17, commit=<optimized out>)
>>   at /usr/src/contrib/jemalloc/include/jemalloc/internal/ehooks.h:208
>> #5  __je_extent_alloc_wrapper (tsdn=tsdn@entry=0x2a2e4060, pac=0x2a601810, ehooks=<optimized out>, new_addr=<optimized out>, size=12288, alignment=4096, zero=true, commit=0xffff6f77, 
>>   growing_retained=<optimized out>) at jemalloc_extent.c:1003
>> #6  0x2a1916e0 in __je_ecache_alloc_grow (tsdn=<optimized out>, tsdn@entry=0x2a2e4060, pac=pac@entry=0x2a601810, ehooks=ehooks@entry=0x2a600080, ecache=<optimized out>, ecache@entry=0x2a603dd0, 
>>   expand_edata=0x0, size=12288, alignment=4096, zero=<optimized out>, guarded=<optimized out>) at jemalloc_extent.c:126
>> #7  0x2a1c9680 in pac_alloc_real (tsdn=0x2a2e4060, pac=0x2a601810, ehooks=0x2a600080, size=12288, alignment=4096, zero=<optimized out>, guarded=false) at jemalloc_pac.c:124
>> #8  pac_alloc_impl (tsdn=tsdn@entry=0x2a2e4060, self=0x2a601810, size=size@entry=12288, alignment=4096, zero=<optimized out>, guarded=false, frequent_reuse=<optimized out>, 
>>   deferred_work_generated=<optimized out>) at jemalloc_pac.c:178
>> #9  0x2a1c7ae8 in pai_alloc (tsdn=0x2a2e4060, self=0x0, size=12288, alignment=2147483615, zero=<optimized out>, guarded=false, frequent_reuse=true, deferred_work_generated=<optimized out>)
>>   at /usr/src/contrib/jemalloc/include/jemalloc/internal/pai.h:43
>> #10 __je_pa_alloc (tsdn=tsdn@entry=0x2a2e4060, shard=shard@entry=0x2a601800, size=12288, alignment=<optimized out>, slab=true, szind=25, zero=<optimized out>, guarded=false, 
>>   deferred_work_generated=0xffff703f) at jemalloc_pa.c:139
>> #11 0x2a16b9f8 in arena_slab_alloc (tsdn=tsdn@entry=0x2a2e4060, arena=0x2a600540, binind=25, binshard=0, bin_info=0x2a21ff0c <__je_bin_infos+1200>) at jemalloc_arena.c:839
>> #12 0x2a16ac98 in __je_arena_cache_bin_fill_small (tsdn=0x2a2e4060, arena=0x2a600540, cache_bin=cache_bin@entry=0x2a2e4528, cache_bin_info=0x2a6004f2, binind=25, nfill=5) at jemalloc_arena.c:1034
>> #13 0x2a1b5694 in __je_tcache_alloc_small_hard (tsdn=0x0, tsdn@entry=0x2a2e4060, arena=0x0, arena@entry=0x2a600540, tcache=tcache@entry=0x2a2e42c8, cache_bin=cache_bin@entry=0x2a2e4528, binind=25, 
>>   tcache_success=0xffff70ef) at jemalloc_tcache.c:238
>> #14 0x2a16cef4 in tcache_alloc_small (tsd=<optimized out>, arena=0x2a600540, tcache=0x2a2e42c8, size=<optimized out>, binind=25, zero=false, slow_path=true)
>>   at /usr/src/contrib/jemalloc/include/jemalloc/internal/tcache_inlines.h:68
>> #15 arena_malloc (tsdn=<optimized out>, arena=<optimized out>, size=1536, ind=25, zero=false, tcache=0x2a2e42c8, slow_path=true)
>>   at /usr/src/contrib/jemalloc/include/jemalloc/internal/arena_inlines_b.h:151
>> #16 0x2a16cb88 in __je_arena_palloc (tsdn=0x0, tsdn@entry=0x2a2e4060, arena=<optimized out>, usize=<optimized out>, usize@entry=1536, alignment=alignment@entry=8, zero=false, tcache=0x2a2e42c8)
>>   at jemalloc_arena.c:1224
>> #17 0x2a16559c in ipallocztm (tsdn=0x2a2e4060, tsdn@entry=0x2a2e42c8, usize=1536, alignment=8, zero=false, tcache=0x2a2e42c8, is_internal=false, arena=0x0)
>>   at /usr/src/contrib/jemalloc/include/jemalloc/internal/jemalloc_internal_inlines_c.h:80
>> #18 ipalloct (tsdn=0x0, tsdn@entry=0x2a2e4060, usize=1536, alignment=8, zero=false, tcache=0x2a2e42c8, arena=0x0)
>>   at /usr/src/contrib/jemalloc/include/jemalloc/internal/jemalloc_internal_inlines_c.h:91
>> #19 0x2a1651f4 in imalloc_no_sample (sopts=0xffff71e4, dopts=0xffff71c4, tsd=0x2a2e4060, size=1536, usize=1536, ind=<optimized out>) at jemalloc_jemalloc.c:2398
>> #20 imalloc_body (sopts=0xffff71e4, dopts=0xffff71c4, tsd=0x2a2e4060) at jemalloc_jemalloc.c:2577
>> #21 0x2a156188 in imalloc (sopts=sopts@entry=0xffff71e4, dopts=<optimized out>, dopts@entry=0xffff71c4) at jemalloc_jemalloc.c:2693
>> #22 0x2a15677c in __aligned_alloc (alignment=8, size=1536) at jemalloc_jemalloc.c:2821
>> #23 0x29e61a00 in std::__1::__libcpp_aligned_alloc[abi:se190107](unsigned int, unsigned int) (__alignment=8, __size=<optimized out>)
>>   at /usr/src/contrib/llvm-project/libcxx/include/__memory/aligned_alloc.h:43
>> #24 operator_new_aligned_impl (size=<optimized out>, alignment=8) at /usr/src/contrib/llvm-project/libcxx/src/new.cpp:129
>> #25 operator new (size=<optimized out>, alignment=<optimized out>) at /usr/src/contrib/llvm-project/libcxx/src/new.cpp:141
>> #26 0x2631dde0 in allocateBuckets () at /usr/src/contrib/llvm-project/llvm/include/llvm/ADT/DenseMap.h:915
>> #27 grow () at /usr/src/contrib/llvm-project/llvm/include/llvm/ADT/DenseMap.h:849
>> #28 0x2631dd0c in grow () at /usr/src/contrib/llvm-project/llvm/include/llvm/ADT/DenseMap.h:580
>> #29 0x2631dd0c in InsertIntoBucketImpl<llvm::BasicBlock const*> () from /usr/lib/libprivatellvm.so.19
>> #30 0x2631daa4 in InsertIntoBucket<llvm::BasicBlock const* const&> () at /usr/src/contrib/llvm-project/llvm/include/llvm/ADT/DenseMap.h:590
>> #31 FindAndConstruct () at /usr/src/contrib/llvm-project/llvm/include/llvm/ADT/DenseMap.h:369
>> #32 0x2631d49c in operator[] () at /usr/src/contrib/llvm-project/llvm/include/llvm/ADT/DenseMap.h:373
>> #33 analyzeBasicBlock () at /usr/src/contrib/llvm-project/llvm/lib/Analysis/CodeMetrics.cpp:234
>> #34 0x28e2c3ec in run () at /usr/src/contrib/llvm-project/llvm/lib/Transforms/IPO/FunctionSpecialization.cpp:643
>> #35 0x28f4fd70 in runIPSCCP () at /usr/src/contrib/llvm-project/llvm/lib/Transforms/IPO/SCCP.cpp:165
>> #36 run () at /usr/src/contrib/llvm-project/llvm/lib/Transforms/IPO/SCCP.cpp:403
>> #37 0x27b85d14 in llvm::detail::PassModel<llvm::Module, llvm::IPSCCPPass, llvm::AnalysisManager<llvm::Module>>::run(llvm::Module&, llvm::AnalysisManager<llvm::Module>&) ()
>>   at /usr/src/contrib/llvm-project/llvm/include/llvm/IR/PassManagerInternal.h:90
>> #38 0x276ee244 in run () at /usr/src/contrib/llvm-project/llvm/include/llvm/IR/PassManagerImpl.h:81
>> #39 0x22174ffc in RunOptimizationPipeline () at /usr/src/contrib/llvm-project/clang/lib/CodeGen/BackendUtil.cpp:1114
>> #40 0x2216cfb8 in EmitAssembly () at /usr/src/contrib/llvm-project/clang/lib/CodeGen/BackendUtil.cpp:1179
>> #41 EmitBackendOutput () at /usr/src/contrib/llvm-project/clang/lib/CodeGen/BackendUtil.cpp:1341
>> #42 0x225cbca0 in HandleTranslationUnit () at /usr/src/contrib/llvm-project/clang/lib/CodeGen/CodeGenAction.cpp:354
>> #43 0x22cff8e4 in ParseAST () at /usr/src/contrib/llvm-project/clang/lib/Parse/ParseAST.cpp:184
>> #44 0x22b5a7b8 in Execute () at /usr/src/contrib/llvm-project/clang/lib/Frontend/FrontendAction.cpp:1078
>> --Type <RET> for more, q to quit, c to continue without paging--
>> #45 0x22adb800 in ExecuteAction () at /usr/src/contrib/llvm-project/clang/lib/Frontend/CompilerInstance.cpp:1061
>> #46 0x22bf6a90 in ExecuteCompilerInvocation () at /usr/src/contrib/llvm-project/clang/lib/FrontendTool/ExecuteCompilerInvocation.cpp:280
>> #47 0x0002afc8 in cc1_main () at /usr/src/contrib/llvm-project/clang/tools/driver/cc1_main.cpp:284
>> #48 0x00038548 in ExecuteCC1Tool () at /usr/src/contrib/llvm-project/clang/tools/driver/driver.cpp:215
>> #49 0x227877ec in operator() () at /usr/src/contrib/llvm-project/llvm/include/llvm/ADT/STLFunctionalExtras.h:68
>> #50 operator() () at /usr/src/contrib/llvm-project/clang/lib/Driver/Job.cpp:440
>> #51 callback_fn<(lambda at /usr/src/contrib/llvm-project/clang/lib/Driver/Job.cpp:440:22)>(void) () at /usr/src/contrib/llvm-project/llvm/include/llvm/ADT/STLFunctionalExtras.h:45
>> #52 0x27d88624 in operator() () at /usr/src/contrib/llvm-project/llvm/include/llvm/ADT/STLFunctionalExtras.h:68
>> #53 RunSafely () at /usr/src/contrib/llvm-project/llvm/lib/Support/CrashRecoveryContext.cpp:426
>> #54 0x22786e90 in Execute () at /usr/src/contrib/llvm-project/clang/lib/Driver/Job.cpp:440
>> #55 0x22748074 in ExecuteCommand () at /usr/src/contrib/llvm-project/clang/lib/Driver/Compilation.cpp:199
>> #56 0x227483d0 in ExecuteJobs () at /usr/src/contrib/llvm-project/clang/lib/Driver/Compilation.cpp:253
>> #57 0x22765bb8 in ExecuteCompilation () at /usr/src/contrib/llvm-project/clang/lib/Driver/Driver.cpp:1943
>> #58 0x00037ba4 in clang_main () at /usr/src/contrib/llvm-project/clang/tools/driver/driver.cpp:391
>> #59 0x000363a8 in main () at /usr/src/usr.bin/clang/clang/clang-driver.cpp:17
> 
> (gdb) list
> 165 assert(size > 0);
> 166 if (config_debug) {
> 167 /* Check the whole first page. */
> 168 size_t *p = (size_t *)addr;
> 169 for (size_t i = 0; i < PAGE / sizeof(size_t); i++) {
> 170 assert(p[i] == 0);
> 171 }
> 
> (gdb) x /1024x addr
> 0x2b629000: 0x00000000 0x00000000 0x00000000 0x00000000
> 0x2b629010: 0x00000000 0x00000000 0x00000000 0x00000000
> 0x2b629020: 0x00000000 0x00000000 0x00000000 0x00000000
> . . .
> 0x2b629c10: 0x00000000 0x00000000 0x00000000 0x00000000
> 0x2b629c20: 0x00000000 0x00000000 0x00000000 0x00000000
> 0x2b629c30: 0x00000000 0x00000000 0x00000000 0x00000000
> 0x2b629c40: 0x5a5a5a5a 0x5a5a5a5a 0x5a5a5a5a 0x5a5a5a5a
> 0x2b629c50: 0x5a5a5a5a 0x5a5a5a5a 0x5a5a5a5a 0x5a5a5a5a
> 0x2b629c60: 0x5a5a5a5a 0x5a5a5a5a 0x5a5a5a5a 0x5a5a5a5a
> . . .
> 0x2b629fd0: 0x5a5a5a5a 0x5a5a5a5a 0x5a5a5a5a 0x5a5a5a5a
> 0x2b629fe0: 0x5a5a5a5a 0x5a5a5a5a 0x5a5a5a5a 0x5a5a5a5a
> 0x2b629ff0: 0x5a5a5a5a 0x5a5a5a5a 0x5a5a5a5a 0x5a5a5a5a
> (gdb) 
> 
> It has more 0x5a5a5a5a 's after that.

The backtrace indicates 3 pages (12288 Bytes, 3072 size_t's) at the
__je_pa_alloc call. So looking
around the beginning and end:

Beginning (and somewhat before):

. . .
0x2b628fc0:	0xa5a5a5a5	0xa5a5a5a5	0xa5a5a5a5	0xa5a5a5a5
0x2b628fd0:	0xa5a5a5a5	0xa5a5a5a5	0xa5a5a5a5	0xa5a5a5a5
0x2b628fe0:	0xa5a5a5a5	0xa5a5a5a5	0xa5a5a5a5	0xa5a5a5a5
0x2b628ff0:	0xa5a5a5a5	0xa5a5a5a5	0xa5a5a5a5	0xa5a5a5a5
(gdb) x /1024x ((size_t*)addr)
0x2b629000:	0x00000000	0x00000000	0x00000000	0x00000000
0x2b629010:	0x00000000	0x00000000	0x00000000	0x00000000
0x2b629020:	0x00000000	0x00000000	0x00000000	0x00000000
. . .

End (and just after):

. . .
0x2b62bfd0:	0x5a5a5a5a	0x5a5a5a5a	0x5a5a5a5a	0x5a5a5a5a
0x2b62bfe0:	0x5a5a5a5a	0x5a5a5a5a	0x5a5a5a5a	0x5a5a5a5a
0x2b62bff0:	0x5a5a5a5a	0x5a5a5a5a	0x5a5a5a5a	0x5a5a5a5a
(gdb) x /1024x ((size_t*)addr)+3072
0x2b62c000:	Cannot access memory at address 0x2b62c000

For reference:

static inline void *
ehooks_alloc(tsdn_t *tsdn, ehooks_t *ehooks, void *new_addr, size_t size,
    size_t alignment, bool *zero, bool *commit) {
        bool orig_zero = *zero;
        void *ret;
        extent_hooks_t *extent_hooks = ehooks_get_extent_hooks_ptr(ehooks);
        if (extent_hooks == &ehooks_default_extent_hooks) {
                ret = ehooks_default_alloc_impl(tsdn, new_addr, size,
                    alignment, zero, commit, ehooks_ind_get(ehooks));
        } else {
                ehooks_pre_reentrancy(tsdn);
                ret = extent_hooks->alloc(extent_hooks, new_addr, size,
                    alignment, zero, commit, ehooks_ind_get(ehooks));
                ehooks_post_reentrancy(tsdn);
        }
        assert(new_addr == NULL || ret == NULL || new_addr == ret);
        assert(!orig_zero || *zero);
        if (*zero && ret != NULL) {
                ehooks_debug_zero_check(ret, size);
        }
        return ret;
}

extent_hooks is optimized out so I do not know the
status for the ehooks_default_alloc_impl vs. the
tsd_pre_reentrancy and extent_hooks->alloc and
ehooks_post_reentrancy usage that actually occurred.

__je_extent_alloc_wrapper's context can be used to find
that *zero was true when ehooks_alloc was called. It
had to be true as of the ehooks_debug_zero_check call.

Nothing suggests a smaller size was involved at any point.

It looks like ehooks_default_alloc_impl or extent_hooks->alloc
(whichever it was) just did not produce the correct content.

Nothing yet stands out to me as looking likely to be somehow
armv7 specific.

Looking at:

void *
ehooks_default_alloc_impl(tsdn_t *tsdn, void *new_addr, size_t size,
    size_t alignment, bool *zero, bool *commit, unsigned arena_ind) {
        arena_t *arena = arena_get(tsdn, arena_ind, false);
        /* NULL arena indicates arena_create. */
        assert(arena != NULL || alignment == HUGEPAGE);
        dss_prec_t dss = (arena == NULL) ? dss_prec_disabled :
            (dss_prec_t)atomic_load_u(&arena->dss_prec, ATOMIC_RELAXED);
        void *ret = extent_alloc_core(tsdn, arena, new_addr, size, alignment,
            zero, commit, dss);
        if (have_madvise_huge && ret) {
                pages_set_thp_state(ret, size);
        }
        return ret;
}

can get into atomic handling: atomic_load_u for ATOMIC_RELAXED
is used. extent_alloc_dss vs. extent_alloc_mmap ends up
involved via extent_alloc_core if ehooks_default_alloc_impl was
used.

I do not see that I can pull out much more based on my lack of
familiarity.

>> For reference:
>> 
>> . . .
>> Building /usr/obj/usr/src-investigation/arm.armv7/lib/clang/libclang/CodeGen/BackendUtil.pico
>> . . .
>> Building /usr/obj/usr/src-investigation/arm.armv7/lib/clang/libclang/CodeGen/CGDecl.pico
>> <jemalloc>: /usr/src/contrib/jemalloc/include/jemalloc/internal/ehooks.h:170: Failed assertion: "p[i] == 0"
>> . . .
>> _ERROR_CMD='c++  -target armv7-gnueabihf-freebsd16.0 --sysroot=/usr/obj/usr/src-investigation/arm.armv7/tmp -B/usr/obj/usr/src-investigation/arm.armv7/tmp/usr/bin -fpic -DPIC  -UPIC -O2 -pipe -fno-common -I/usr/obj/usr/src-investigation/arm.armv7/lib/clang/libclang -I/usr/obj/usr/src-investigation/arm.armv7/lib/clang/libllvm -I/usr/src-investigation/contrib/llvm-project/clang/lib/Basic -I/usr/src-investigation/contrib/llvm-project/clang/lib/Driver -I/usr/src-investigation/contrib/llvm-project/clang/lib/CodeGen -I/usr/src-investigation/contrib/llvm-project/clang/include -DCLANG_ENABLE_ARCMT -DCLANG_ENABLE_STATIC_ANALYZER -I/usr/src-investigation/lib/clang/include -I/usr/src-investigation/contrib/llvm-project/llvm/include -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -DHAVE_VCS_VERSION_INC -DLLVM_DEFAULT_TARGET_TRIPLE=\"armv7-unknown-freebsd16.0-gnueabihf\" -DLLVM_HOST_TRIPLE=\"armv7-unknown-freebsd16.0\" -DDEFAULT_SYSROOT=\"\" -DLLVM_TARGET_ENABLE_AARCH64 -DLLVM_TARGET_ENABLE_ARM -DLLVM_TARGET_ENABLE_POWERPC -DLLVM_TARGET_ENABLE_RISCV -DLLVM_TARGET_ENABLE_X86 -DLLVM_NATIVE_ASMPARSER=LLVMInitializeARMAsmParser -DLLVM_NATIVE_ASMPRINTER=LLVMInitializeARMAsmPrinter -DLLVM_NATIVE_DISASSEMBLER=LLVMInitializeARMDisassembler -DLLVM_NATIVE_TARGET=LLVMInitializeARMTarget -DLLVM_NATIVE_TARGETINFO=LLVMInitializeARMTargetInfo -DLLVM_NATIVE_TARGETMC=LLVMInitializeARMTargetMC -ffunction-sections -fdata-sections -gline-tables-only -Wno-format-zero-length -fstack-protector-strong -Wdate-time -Wno-empty-body -Wno-string-plus-int -Wno-unused-const-variable -Wno-error=unused-but-set-parameter -Wno-error=cast-function-type-mismatch -Wno-tautological-compare -Wno-unused-value -Wno-parentheses-equality -Wno-unused-function -Wno-enum-conversion -Wno-unused-local-typedef -Wno-address-of-packed-member -Wno-switch -Wno-switch-enum -Wno-knr-promoted-parameter -Wno-parentheses -Qunused-arguments   -fno-exceptions -fno-rtti -gline-tables-only -std=c++17    -stdlib=libc++     -c /usr/src-investigation/contrib/llvm-project/clang/lib/CodeGen/BackendUtil.cpp -o CodeGen/BackendUtil.pico;'


===
Mark Millard
marklmi at yahoo.com