Wrong prefix checking of global variables

[Pavel Kopyl]

Hello,

I agree, better to use POSIX compatible features.

-Pavel

On 01/25/2016 11:40 PM, Marc Glisse wrote:
> On Mon, 25 Jan 2016, Pavel Kopyl wrote:
>
>> Hello,
>>
>> I faced with the situation where ./configure makes wrong decision 
>> about if global variables should be prefixed or not.
>>
>> Conditions.
>>
>> Version:             trunk (GNU MP 6.1.99)
>> Host type:         armv7l-unknown-linux-gnueabi
>> Compiler:          Linaro GCC 4.9.2
>>
>> ./configure \
>>    --prefix=/usr \
>>    --includedir=/usr/include \
>>    --libdir=/usr/lib \
>>    --enable-cxx \
>>
>>
>> To check if a global variable should be prefixed with underscore 
>> ./configure "greps" variable's name in object file in the following 
>> test:
>>
>> cat conftest.c
>> int gurkmacka;
>>
>>
>> cat configure
>> ..
>> $NM conftest.$OBJEXT >conftest.out
>>  if grep _gurkmacka conftest.out >/dev/null; then
>>    gmp_cv_asm_underscore=yes
>>  elif grep gurkmacka conftest.out >/dev/null; then
>>    gmp_cv_asm_underscore=no
>>  else
>>    echo "configure: $NM doesn't have gurkmacka:" >&5
>>    cat conftest.out >&5
>> ...
>>
>> Generally it works fine, but being built with enabled 
>> AddressSanitizer (-fsanitize=address, -fno-common), compiler 
>> generates instrumented code and
>> object file contains additional symbols whose names may incorporate 
>> "_gurkmacka" as a substring, though actually global variable is not 
>> prefixed.
>>
>> Lets see an example:
>>
>> Without AddressSanitizer:
>>
>> cat conftest.out
>> 00000004 C gurkmacka
>>
>>
>> With AddressSanitizer:
>>
>> cat conftest.out
>> 00000000 t _GLOBAL__sub_D_00099_0_gurkmacka
>> 00000000 t _GLOBAL__sub_I_00099_1_gurkmacka
>>         U __aeabi_unwind_cpp_pr0
>>         U __asan_init
>>         U __asan_register_globals
>>         U __asan_unregister_globals
>>         U __asan_version_mismatch_check_v6
>> 00000000 B gurkmacka
>>
>> Based on the former example ./configure erroneously assumes that 
>> global variables should be prefixed.**
>>
>> Attached patch fixes this issue.
>
> Hello,
>
> thank you for the description and the patch. IIRC, \<\> is not a 
> standard feature of grep but a GNU extension. How portable is it?
>

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