+++ /dev/null
-The collector uses a large amount of conditional compilation in order to
-deal with platform dependencies. This violates a number of known coding
-standards. On the other hand, it seems to be the only practical way to
-support this many platforms without excessive code duplication.
-
-A few guidelines have mostly been followed in order to keep this manageable:
-
-1) #if and #ifdef directives are properly indented whenever easily possible.
-All known C compilers allow whitespace between the "#" and the "if" to make
-this possible. ANSI C also allows white space before the "#", though we
-avoid that. It has the known disadvantages that it differs from the normal
-GNU conventions, and that it makes patches larger than otherwise necessary.
-In my opinion, it's still well worth it, for the same reason that we indent
-ordinary "if" statements.
-
-2) Whenever possible, tests are performed on the macros defined in gcconfig.h
-instead of directly testing patform-specific predefined macros. This makes it
-relatively easy to adapt to new compilers with a different set of predefined
-macros. Currently these macros generally identify platforms instead of
-features. In many cases, this is a mistake.
-
-3) The code currently avoids #elif, eventhough that would make it more
-readable. This was done since #elif would need to be understood by ALL
-compilers used to build the collector, and that hasn't always been the case.
-It makes sense to reconsider this decision at some point, since #elif has been
-standardized at least since 1989.
-
-Many of the tested configuration macros are at least somewhat defined in
-either include/private/gcconfig.h or in Makefile.direct. Here is an attempt
-at defining some of the remainder: (Thanks to Walter Bright for suggesting
-this. This is a work in progress)
-
-MACRO EXPLANATION
------ -----------
-
-__DMC__ Always #define'd by the Digital Mars compiler. Expands
- to the compiler version number in hex, i.e. 0x810 is
- version 8.1b0
-
-_ENABLE_ARRAYNEW
- #define'd by the Digital Mars C++ compiler when
- operator new[] and delete[] are separately
- overloadable. Used in gc_cpp.h.
-
-_MSC_VER Expands to the Visual C++ compiler version. Assumed to
- not be defined for other compilers (at least if they behave
- appreciably differently).
-
-_DLL Defined by Visual C++ if dynamic libraries are being built
- or used. Used to test whether __declspec(dllimport) or
- __declspec(dllexport) needs to be added to declarations
- to support the case in which the collector is in a dll.
-
-GC_DLL User-settable macro that forces the effect of _DLL.
-
-GC_NOT_DLL User-settable macro that overrides _DLL, e.g. if dynamic
- libraries are used, but the collector is in a static library.
-
-__STDC__ Assumed to be defined only by compilers that understand
- prototypes and other C89 features. Its value is generally
- not used, since we are fine with most nonconforming extensions.
-
-SUNOS5SIGS Solaris-like signal handling. This is probably misnamed,
- since it really doesn't guarantee much more than Posix.
- Currently set only for Solaris2.X, HPUX, and DRSNX. Should
- probably be set for some other platforms.
-
-PCR Set if the collector is being built as part of the Xerox
- Portable Common Runtime.
-
-SRC_M3 Set if the collector is being built as a replacement of the
- one in the DEC/Compaq SRC Modula-3 runtime. I suspect this
- was last used around 1994, and no doubt broke a long time ago.
- It's there primarily incase someone wants to port to a similar
- system.
-
-
-
projects / msp430-gcc.git / blobdiff