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Diffstat (limited to 'README')
| -rw-r--r-- | README | 100 |
1 files changed, 11 insertions, 89 deletions
@@ -1,93 +1,15 @@ -Building RTEMS -============== -See the file README.configure. +See the documentation manuals in doc/ with daily builds available online at +http://rtems.org/onlinedocs/doc-current/share/rtems/html/ and released builds +at http://www.rtems.org/onlinedocs/releases/ -Directory Overview -================== +See the RTEMS Wiki at http://wiki.rtems.org/wiki/index.php/Main_Page +for community knowledge and tutorials. -This is the top level of the RTEMS directory structure. The following -is a description of the files and directories in this directory: +RTEMS Doxygen available at http://www.rtems.org/onlinedocs/doxygen/cpukit/html - INSTALL - Rudimentary installation instructions. For more detailed - information please see the Release Notes. The Postscript - version of this manual can be found in the file - c_or_ada/doc/relnotes.tgz. +Get help on the mailing lists: +* For general-purpose questions related to using RTEMS, use the + rtems-users ml: http://www.rtems.org/mailman/listinfo/rtems-users +* For questions and discussion related to development of RTEMS, use the + rtems-devel ml: http://www.rtems.org/mailman/listinfo/rtems-devel - LICENSE - Required legalese. - - README - This file. - - c - This directory contains the source code for the C - implementation of RTEMS as well as the test suites, sample - applications, Board Support Packages, Device Drivers, and - support libraries. - - doc - This directory contains the PDL for the RTEMS executive. - -Ada versus C -============ - -There are two implementations of RTEMS in this source tree -- -in Ada and in C. These two implementations are functionally -and structurally equivalent. The C implementation follows -the packaging conventions and hierarchical nature of the Ada -implementation. In addition, a style has been followed which -allows one to easily find the corresponding Ada and C -implementations. - -File names in C and code placement was carefully designed to insure -a close mapping to the Ada implementation. The following file name -extensions are used: - - .adb - Ada body - .ads - Ada specification - .adp - Ada body requiring preprocessing - .inc - include file for .adp files - - .c - C body (non-inlined routines) - .inl - C body (inlined routines) - .h - C specification - -In the executive source, XYZ.c and XYZ.inl correspond directly to a -single XYZ.adb or XYZ.adp file. A .h file corresponds directly to -the .ads file. There are only a handful of .inc files in the -Ada source and these are used to insure that the desired simple -inline textual expansion is performed. This avoids scoping and -calling convention side-effects in carefully constructed tests -which usually test context switch behavior. - -In addition, in Ada code and data name references are always fully -qualified as PACKAGE.NAME. In C, this convention is followed -by having the package name as part of the name itself and using a -capital letter to indicate the presence of a "." level. So we have -PACKAGE.NAME in Ada and _Package_Name in C. The leading "_" in C -is used to avoid naming conflicts between RTEMS and user variables. -By using these conventions, one can easily compare the C and Ada -implementations. - -The most noticeable difference between the C and Ada83 code is -the inability to easily obtain a "typed pointer" in Ada83. -Using the "&" operator in C yields a pointer with a specific type. -The 'Address attribute is the closest feature in Ada83. This -returns a System.Address and this must be coerced via Unchecked_Conversion -into an access type of the desired type. It is easy to view -System.Address as similar to a "void *" in C, but this is not the case. -A "void *" can be assigned to any other pointer type without an -explicit conversion. - -The solution adopted to this problem was to provide two routines for -each access type in the Ada implementation -- one to convert from -System.Address to the access type and another to go the opposite -direction. This results in code which accomplishes the same thing -as the corresponding C but it is easier to get lost in the clutter -of the apparent subprogram invocations than the "less bulky" -C equivalent. - -A related difference is the types which are only in Ada which are used -for pointers to arrays. These types do not exist and are not needed -in the C implementation. |