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This commits the result of running gdb/copyright.py as per our Start
of New Year procedure...
gdb/ChangeLog
Update copyright year range in copyright header of all GDB files.
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The gdb_mpz class currently provides a couple of methods which
essentially export an mpz_t value into either a buffer, or an integral
type. The export is based on using the mpz_export function which
we discovered can be a bit treacherous if used without caution.
In particular, the initial motivation for this patch was to catch
situations where the mpz_t value was so large that it would not fit
in the destination area. mpz_export does not know the size of
the buffer, and therefore can happily write past the end of our buffer.
While designing a solution to the above problem, I also discovered
that we also needed to be careful when exporting signed numbers.
In particular, numbers which are larger than the maximum value
for a given signed type size, but no so large as to fit in the
*unsigned* version with the same size, would end up being exported
incorrectly. This is related to the fact that mpz_export ignores
the sign of the value being exportd, and assumes an unsigned export.
Thus, for such large values, the appears as if mpz_export is able
to fit our value into our buffer, but in fact, it does not.
Also, I noticed that gdb_mpz::write wasn't taking its unsigned_p
parameter, which was a hole.
For all these reasons, a new low-level private method called
"safe_export" has been added to class gdb_mpz, whose goal is
to perform all necessary checks and manipulations for a safe
and correct export. As a bonus, this method allows us to factorize
the handling of negative value exports.
The gdb_mpz::as_integer and gdb_mpz::write methods are then simplified
to take advantage of this new safe_export method.
gdb/ChangeLog:
* gmp-utils.h (gdb_mpz::safe_export): New private method.
(gdb_mpz::as_integer): Reimplement using gdb_mpz::safe_export.
* gmp-utils.c (gdb_mpz::write): Rewrite using gdb_mpz::safe_export.
(gdb_mpz::safe_export): New method.
* unittests/gmp-utils-selftests .c (gdb_mpz_as_integer):
Update function description.
(check_as_integer_raises_out_of_range_error): New function.
(gdb_mpz_as_integer_out_of_range): New function.
(_initialize_gmp_utils_selftests): Register
gdb_mpz_as_integer_out_of_range as a selftest.
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This commit changes the interfaces of some of the methods declared
in gmp-utils to take a gdb::array_view of gdb_byte instead of a
(gdb_byte *, size) couple.
This makes these methods' API probably more C++-idiomatic.
* gmp-utils.h (gdb_mpz::read): Change buf and len parameters
into one single gdb::array_view parameter.
(gdb_mpz::write): Likewise.
(gdb_mpq::read_fixed_point, gdb_mpq::write_fixed_point): Likewise.
* gmp-utils.c (gdb_mpz::read): Change buf and len parameters
into one single gdb::array_view parameter.
Adjust implementation accordingly.
(gdb_mpz::write): Likewise.
(gdb_mpq::read_fixed_point, gdb_mpq::write_fixed_point): Likewise.
* unittests/gmp-utils-selftests.c: Adapt following changes above.
* valarith.c, valops.c, valprint.c, value.c: Likewise.
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When building GDB using Ubuntu 20.04's system libgmp and compiler,
running the "maintenance selftest" command triggers the following error:
| Running selftest gdb_mpq_write_fixed_point.
| *** stack smashing detected ***: terminated
| [1] 1092790 abort (core dumped) ./gdb gdb
This happens while trying to construct an mpq_t object (a rational)
from two integers representing the numerator and denominator.
In our test, the numerator is -8, and the denominator is 1.
The problem was that the rational was constructed using the wrong
function. This is what we were doing prior to this patch:
mpq_set_ui (v.val, numerator, denominator);
The 'u' in "ui" stands for *unsigned*, which is wrong because
numerator and denominator's type is "int".
As a result of the above, instead of getting a rational value of -8,
we get a rational with a very large positive value (gmp_printf
says "18446744073709551608").
From there, the test performs an operation which is expected to
write this value into a buffer which was not dimensioned to fit
such a number, thus leading GMP into a buffer overflow.
This was verified by applying the formula that GMP's documentation
gives for the required memory buffer size needed during export:
| When an application is allocating space itself the required size can
| be determined with a calculation like the following. Since
| mpz_sizeinbase always returns at least 1, count here will be at
| least one, which avoids any portability problems with malloc(0),
| though if z is zero no space at all is actually needed (or written).
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| numb = 8*size - nail;
| count = (mpz_sizeinbase (z, 2) + numb-1) / numb;
| p = malloc (count * size);
With the very large number, mpz_sizeinbase returns 66 and thus
the malloc size becomes 16 bytes instead of the 8 we allocated.
This patch fixes the issue by using the correct "set" function.
gdb/ChangeLog:
* unittests/gmp-utils-selftests.c (write_fp_test): Use mpq_set_si
instead of mpq_set_ui to initialize our GMP rational.
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When building on solaris (gcc farm machine gcc211), I get:
CXX unittests/gmp-utils-selftests.o
/export/home/simark/src/binutils-gdb/gdb/unittests/gmp-utils-selftests.c: In function 'void selftests::gdb_mpz_read_all_from_small()' :
/export/home/simark/src/binutils-gdb/gdb/unittests/gmp-utils-selftests.c:128:43: error: call of overloaded 'pow(int, int)' is ambiguous
LONGEST l_min = -pow (2, buf_len * 8 - 1);
^
In file included from /opt/csw/lib/gcc/sparc-sun-solaris2.10/5.5.0/include-fixed/math.h:22:0,
from ../gnulib/import/math.h:27,
from /export/home/simark/src/binutils-gdb/gdb/unittests/gmp-utils-selftests.c:23:
/opt/csw/lib/gcc/sparc-sun-solaris2.10/5.5.0/include-fixed/iso/math_iso.h:210:21: note: candidate: long double std::pow(long double, long double)
inline long double pow(long double __X, long double __Y) { return
^
/opt/csw/lib/gcc/sparc-sun-solaris2.10/5.5.0/include-fixed/iso/math_iso.h:170:15: note: candidate: float std::pow(float, float)
inline float pow(float __X, float __Y) { return __powf(__X, __Y); }
^
/opt/csw/lib/gcc/sparc-sun-solaris2.10/5.5.0/include-fixed/iso/math_iso.h:71:15: note: candidate: double std::pow(double, double)
extern double pow __P((double, double));
^
The "pow" function overloads only exist for float-like types, and the
compiler doesn't know which one we want. Change "2" for "2.0", which
makes the compiler choose one alternative (the double one, I believe).
gdb/ChangeLog:
* unittests/gmp-utils-selftests.c (gdb_mpz_read_all_from_small):
Pass 2.0 to pow.
(gdb_mpz_write_all_from_small): Likewise.
Change-Id: Ied2ae0f01494430244a7c94f8a38b07d819f4213
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This API was motivated by a number of reasons:
- GMP's API does not handle "long long" and "unsigned long long",
so using LONGEST and ULONGEST is not straightforward;
- Automate the need to initialize GMP objects before use, and
clear them when no longer used.
However, this API grew also to help with similar matter such
as formatting to a string, and also reading/writing fixed-point
values from byte buffers.
Dedicated unit testing is also added.
gdb/ChangeLog:
* gmp-utils.h, gmp-utils.h: New file.
* unittests/gmp-utils-selftests.c: New file.
* Makefile.in (SUBDIR_UNITTESTS_SRCS): Add
unittests/gmp-utils-selftests.c.
(COMMON_SFILES) Add gmp-utils.c.
(HFILES_NO_SRCDIR): Add gmp-utils.h.
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