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Re: [PATCH] linux-user: limit check to HOST_LONG_BITS == 32
From: |
Alex Bennée |
Subject: |
Re: [PATCH] linux-user: limit check to HOST_LONG_BITS == 32 |
Date: |
Thu, 21 May 2020 13:32:41 +0100 |
User-agent: |
mu4e 1.4.6; emacs 28.0.50 |
Peter Maydell <address@hidden> writes:
> On Thu, 21 May 2020 at 11:22, Alex Bennée <address@hidden> wrote:
>>
>> Newer clangs rightly spot that you can never exceed the full address
>> space of 64 bit hosts with:
>>
>> linux-user/elfload.c:2076:41: error: result of comparison 'unsigned
>> long' > 18446744073709551615 is always false
>> [-Werror,-Wtautological-type-limit-compare]
>> 4685 if ((guest_hiaddr - guest_base) > ~(uintptr_t)0) {
>> 4686 ~~~~~~~~~~~~~~~~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~
>> 4687 1 error generated.
>>
>> So lets limit the check to 32 bit hosts only.
>>
>> Fixes: ee94743034bf
>> Reported-by: Thomas Huth <address@hidden>
>> Signed-off-by: Alex Bennée <address@hidden>
>> ---
>> linux-user/elfload.c | 2 ++
>> 1 file changed, 2 insertions(+)
>>
>> diff --git a/linux-user/elfload.c b/linux-user/elfload.c
>> index 01a9323a637..797fbf2337a 100644
>> --- a/linux-user/elfload.c
>> +++ b/linux-user/elfload.c
>> @@ -2072,6 +2072,7 @@ static void pgb_have_guest_base(const char
>> *image_name, abi_ulong guest_loaddr,
>> image_name, (uint64_t)guest_hiaddr, reserved_va);
>> exit(EXIT_FAILURE);
>> }
>> +#if HOST_LONG_BITS == 32
>> } else {
>> if ((guest_hiaddr - guest_base) > ~(uintptr_t)0) {
>> error_report("%s: requires more virtual address space "
>> @@ -2079,6 +2080,7 @@ static void pgb_have_guest_base(const char
>> *image_name, abi_ulong guest_loaddr,
>> image_name, (uint64_t)guest_hiaddr - guest_base);
>> exit(EXIT_FAILURE);
>> }
>> +#endif
>
> Could we write this so that we have the #if...#endif
> conditional nested inside the if { ... } else { ... },
> rather than having the two conditional constructs
> oddly intermeshed?
Sure - I thought the compiler would complain about having an empty else
leg but I've just checked and it doesn't seem to care.
>
> thanks
> -- PMM
--
Alex Bennée