GMP 4.2 is upwardly binary compatible with older 4.x, and 3.x versions.

New features of GMP 4.2.2

• License is now LGPL version 3.

• Shared library numbers corrected for libcxx.
• Fixed serious bug in gmpxx.h where a=a+b*c would generate garbage. Note that this only affects C++ programs.
• Fix crash in mpz_set_d for arguments with large negative exponent.
• Fix 32-bit ABI bug with Itanium assembly for popcount and hamdist.
• Fix assembly syntax problem for powerpc-ibm-aix with AIX native assembler.
• Fix problems with x86 --enable-fat, where the compiler was told to generate code for the build machine, not plain i386 code as it should.
• Improved recognition of powerpc systems wrt Altivec/VMX capability.
• Misc minor fixes, mainly workarounds for compiler/assembler bugs.

• "Core 2" and Pentium 4 processors, running in 64-bit mode will get a slight boost as they are now specifically recognized.

• New support for x86_64-solaris
• New, rudimentary support for x86-apple-darwin and x86_64-apple-darwin. (Please see http://gmplib.org/macos.html for more information.)

New features of GMP 4.2.1

• Shared library numbers corrected.
• Broken support for 32-bit AIX fixed.
• Bug fixed in hamdist/popcount for powerpc64 mode32.
• Misc minor fixes.

• Exact division (mpz_divexact) now falls back to plain division for large operands.

• Support for some new systems.

New features of GMP 4.2

• Minor bug fixes and code generalizations.

• Many minor optimizations, too many to mention here.
• Division now always subquadratic.
• Computation of n-factorial much faster.
• Added basic x86-64 assembly code.
• Floating-point output is now subquadratic for all bases.
• FFT multiply code now about 25% faster.
• Toom3 multiply code faster.

• Much improved configure.
• Temporary allocations are now made on the stack only if small.
• New systems supported: HPPA-2.0 gcc, IA-64 HP-UX, PowerPC-64 Darwin, Sparc64 GNU/Linux.
• New i386 fat binaries, selecting optimised code at runtime (--enable-fat).
• New build option: --enable-profiling=instrument.
• New memory function: mp_get_memory_functions.
• New Mersenne Twister random numbers: gmp_randinit_mt, also now used for gmp_randinit_default.
• New random functions: gmp_randinit_set, gmp_urandomb_ui, gmp_urandomm_ui.
• New integer functions: mpz_combit, mpz_rootrem.
• gmp_printf etc new type "M" for mp_limb_t.
• gmp_scanf and friends now accept C99 hex floats.
• Numeric input and output can now be in bases up to 62.
• Comparisons mpz_cmp_d, mpz_cmpabs_d, mpf_cmp_d recognise infinities.
• Conversions mpz_get_d, mpq_get_d, mpf_get_d truncate towards zero, previously their behaviour was unspecified.
• Fixes for overflow issues with operands >= 2³¹ bits.

• mpfr is gone, and will from now on be released only separately. Please see the MPFR web pages.