Release 2.6, 2015-12-21

Usability:

Generation of full DWARF v2 debugging information in "-g" mode,
including function-local variables. This is fully supported
for the PowerPC target with GNU tools or Diab tools. Support
for IA32 and ARM is nearly there.
Production of detailed explanations for syntax errors during parsing.
(Exploiting recent work by F. Pottier on the Menhir parser generator.)
PowerPC port: added many new builtin functions.

Support for PowerPC 64-bits (pointers are still 32-bit wide)
and Freescale's E5500 variant.
More prudent alias analysis for operations over pointers that are
formally undefined, such as bit masking.
New pass: Debugvar, to associate debug information to local variables.

Richer representation of arguments and results to builtin operations.
As a consequence, annotation builtins no longer need special handling.
Added EF_debug builtins to transport debugging information throughout
the compiler back-end.
Upgraded the Flocq library to version 2.5.0.

Issue #71: incorrect initialization of an array of wchar_t
Corrected the handling of bit-fields of type _Bool and width > 1
Removed copy optimization when returning a struct from a function.
Full parsing of unprototyped (K&R-style) function definitions.
(Before, the parsing was incomplete and would reject some definitions.)

The cchecklink tool (for a posteriori validation of assembly
and linking) was removed. It is replaced by the Valex tool,
available from AbsInt.
Added a command-line option -conf to select
a different compcert.ini configuration file.
Removed the command-line options fstruct-passing=
and -fstruct-return=, more confusing than useful.
Added a command-line option -fstruct-passing that activates
ABI-conformant by-value passing of structs and unions as
function arguments or results. If this option is not set,
passing a struct/union as function argument is now rejected.
The -fstruct-return command-line option is deprecated and
becomes a synonymous for -fstruct-passing.
The return type of __builtin_clz() is int, as documented,
and not unsigned int, as previously implemented.