This is a follow-up patch for Sandra Loosemore's patch in this thread: "reimplement -fstrict-volatile-bitfields, v3".
It was already posted a few weeks ago, but in the wrong thread. Therefore I re-post it herewith. It was initially suggested by Hans-Peter Nilsson, and I had much help from him in putting everything together. Thanks again H-P. Here is a short specification: The -Wportable-volatility warning is an optional warning, to warn about code for which separate incompatbile definitions on different platforms (or between C and C++) exist even within gcc. It will be usable for driver code you want to be portable on different architectures. This warning should only be emitted if the code is significantly different when -fstrict-volatile-bitfields is used or not. It should not be emitted for the code which is not affected by this option. In other words, it should be emitted on all bit-fields when the definition or the context is volatile, except when the whole structure is not AAPCS ABI compliant, i.e. packed or unaligned. On the other hand you should always get the same warnings if you combine -Wportable-volatility with -fstrict-volatile-bitfields or not. And of course it should not depend on the specific target that is used to compile. I boot-strapped this on a i686-pc-linux-gnu and all Wportable-volatility test cases are passed for C and C++. Additionally I used a cross-compiler for arm-eabi to manually cross-check that the warnings are independent of the target platform. Regards Bernd Edlinger
2013-09-03 Bernd Edlinger <bernd.edlin...@hotmail.de>
Implement -Wportable-volatility warning to warn about
code which accesses volatile structure members for
which different ABI specifications exist.
* expr.c (check_portable_volatility): New function.
(expand_assignment): call check_portable_volatility.
(expand_real_expr_1): Likewise.
* fold-const.c (optimize_bit_field_compare): Handle
warn_portable_volatility. Removed if-statement, because
condition "flag_strict_volatile_bitfields > 0" is always false.
* stor-layout.c (layout_decl): Handle warn_portable_volatility.
* c-family/c.opt: Add -Wportable-volatility option.
* doc/invoke.texi: Add documentation about -Wportable-volatility.
testsuite:
c-c++-common/
* Wportable-volatility-1.c: New testcase.
* Wportable-volatility-2.c: New testcase.
patch-portable-volatility.diff
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