CompCert Release 15.10
----------------------

DWARF support
-------------
DWARF2 debugging information is now written for the Diab and GCC backends.

New language features
---------------------
* Added an implicit "return 0" for main() without return.
* Set and clear the CR6 bit before calling an unprototyped
  function to support unprototyped variable argument functions.
* Fixed issue with parsing of type names which occur
  if a typedef name is used after a for loop that uses
  the same name for a loop variable.
* Allow redefinitions of typedefs with the same name and same type
  as specified in ISO/IEC 9899:201x 6.7p3 bullet point 1.
* Added support for bitfield members in unions.

New built-in functions
----------------------
Note: the built-ins are for a PPC architecture in embedded mode only.

- __builtin_set_spr(spr,val)
  Moves "val" to special purpose register "spr"

- result = __builtin_get_spr(spr)
  Returns the value of the special purpose register "spr" in "result"

- __builtin_prefetch(ea,rw=0/1,ct=0/1/2)
  Data Cache Block (rw=0) or
  Data Cache Block for Store (rw=1)

- __builtin_dcbf(ea)
  Data Cache Block Flush

- __builtin_dcbt(ea)
  Data Cache Block Touch

- __builtin_dcbtls(ea,ct=0/2)
  Data Cache Block Touch and Lock Set

- __builtin_dcbi(ea)
  Data Cache Block Invalidate

- __builtin_dcbz(ea)
  Data Cache Block set to Zero

- __builtin_icbtls(ea,ct=0/2)
  Instruction Cache Block Touch and Lock Set

- __builtin_icbi(ea)
  Instruction Cache Block Invalidate

- __builtin_mbar(mo=0/1)
  Memory Barrier

- __builtin_isync()
  Instruction Synchronize

- __builtin_sync() / __builtin_lwsync
  Synchronize

- __builtin_cmpb(result,a,b)
  Compare Bytes

- __atomic_exchange(ea0,ea1,result)
  Atomic Exchange:
  stores the contents of "*ea1" into "*ea0"
  while the original value of "*ea0" is copied to "*result"

- result = __atomic_compare_exchange(ea,expected,desired)

  Atomic Compare and Exchange:
  compares the content of "*ea" to that of "*expected";
  if these are equal, the operation is a read-modify-write
  that writes "*desired" into "*ea" and the returned value
  "result" is "1"; if they are not equal, the operation is
  a read and the current content of "*ea" is written into
  "*expected" while the returned value "result" is "0"

- __atomic_load(source,destination)
  Atomic Load:
  returns the contents of "*source" in "*destination"

- result = __sync_fetch_and_add(ea,val)
  Syncronize Fetch and Add:
  increments the content of "*ea" by "val" and returns
  the previous value of "*ea"

- result = __builtin_clz(val)
  Count Leading Zeros in "val"

- result = __builtin_isel(e, vala, valb)
  Returns "vala" if the given boolean expression "e" is true,
  and "valb" otherwise

Valex
-----
* Added the Valex tool for postpass validation of the executable
  assembled/linked with the WindRiver Diab or GCC toolchain.
* New serialization of the assembler AST in ".json" format.
* Static functions are renamed to avoid name clashes;
  "<f>" becomes "_<file>_<f>".

Fixes
-----
* Faster parsing of floating point numbers with large exponents.
* Subtraction of two pointers produces now a signed result.
* When assigning to a bit field of type "_Bool",
  the right-hand side is now normalized to "0" or "1"
  via a cast to "_Bool".
* Fixed the printing of assembly output of the "stwux"
  and "cntlzw" instructions.
* Reject non-void functions with incomplete return types.
* Reject more cases of unstructured control flow in switch statements.
* Resolved issue with struct return to an overlapping struct.
* The implict type of the wchar_t type and the typedef
  in the stddef header are now compatible to the WindRiver
  Diab C compiler.
* More conservative pointer analysis to avoid optimizations
  on code that casts pointer to integer and back.

Usability
---------
* CompCert standard headers no longer lead to incompatible
  type definitions.
* Added support for anonymous structs and unions in the debug type
  information as well as forward declarations of structs and unions.
* CompCert now writes its build number along with a version string
  and compile-time options to the generated assembler files and into
  the Dwarf debugging information.

Known issues
------------
If any of the following features are used, code correctness cannot
be guaranteed in the current version of CompCert and must be checked
separately.

* External variable declarations in block scope are not supported.
* The result of casts between pointer and integer types with sizes
  other than 32 bit are undefined in the CompCert C semantics.
* The bitfield layout of CompCert is incompatible with the bitfield
  layout of the WindRiver Diab C compiler.
* Function parameters of type "float" that are passed
  via the stack are passed as 4-byte single precision values.
  This behaviour differs from that of the Windriver Diab C compiler,
  which converts float arguments to double precision when passing
  them via the stack.
* Types introduced in sizeof and cast expressions cannot be used
  after said expressions. The scopes are not correct.
* CompCert may fail to parse empty initializer lists for array variables.
* Wide string literals are parsed incorrectly when they contain
  non-ASCII wide characters.
* Compcert currently cannot compile K&R functions with incompatible
  prototype definitions.
* CompCert may fail to parse (partial) initialization of multi-dimensional
  arrays if braces are missing.
* Compiling several C files with debug information at once may fail.


==============================================================================
Last modified on 9 October 2015 by alex@absint.com.
Copyright 2015 AbsInt. www.absint.com
==============================================================================
An HTML version of these release notes is available at
www.absint.com/releasenotes/compcert/15.10