Borland C++ 5.0 RTL fix

There is a bug in the heap manager in Borland C++ 5.x, and in C++ Builder up to 4.0. It can result in program crashes when allocating and deallocating large chunks of memory. There were discussions about the bug in Borland newsgroups, which can be found with Google group search with the keyword bts-13191. This bug is fixed in C++ Builder 5.0.

To apply the fix to Borland C++ 5.0, first copy the run-time library source from the instalation CD. It is located in \BC5\SOURCE\RTL.
Note: The version of Borland C++ 5.02 included with Borland C++ Builder does not come with RTL sources.

Then two modifications must be made in RTL source in the file MEMORY\COMMON32\HEAP.C:
  1. In the function _get_more_heap(), line 473, replace the code
    if (_virt_reserve(MAX(_virt_heap_size, aMinSize), &v, &vsize) == 0)
    if (_virt_reserve(MAX(_virt_heap_size, aMinSize+PAGESIZE), &v, &vsize) == 0) /* fix for bts-37621 */

  2. In the function _release_heap_at(), line 589, replace the code
    _virt_decommit(h->sysBlocks[h->numSysBlocks - 1] + newSize, h->cSize - newSize);
    _virt_decommit(((char *) h) + newSize, h->cSize - newSize); /* fix for bts-13191 */

In the makefiles for rebuilding the RTL there is a bug which leads to generation of incorrect CW3230.DLL and CW3230MT.DLL. The bug is that the module XX.OBJ is included twice in the command line passed to TLINK32.
To fix the problem, edit the file RTL\SOURCE\EXCEPT\COMMON32\MAKEFILE and remove the line containing XX.OBJ.

Note that for full rebuild of the RTL, there must be about 100-150 MB free disk space.
You will also need TASM32 to build the .asm files. It can be aquired from Borland C++ Builder 6 for example, and TASM32.EXE can be copied in the BC5\BIN folder.
Start MS-DOS prompt, go to \BC5\SOURCE\RTL, and execute the commands
(If Borland C++ is install in folder different from C:\BC5, change the commands accordingly)
The lines
Setting LOGFILE to log\win32.log!
Building Win32 libraries
should be reported, and then the build process will go for a while without visible output.

When finished, examine the file RTL\LOG\WIN32.LOG to see if there are any erros encountered during the build.
If there are no problems, copy the files CW3230*.DLL to BC5\BIN and CW*.LIB to BC5\LIB.

If the build failed, and the log file reports Error E2209 C:\BC5\include\stddefs.h 50: Unable to open include file 'cstddef', a likely reason is that in the PATH is a path to recent Borland compiler preceeding the BC5 one. To correct this, try the command SET PATH=C:\BC5\BIN;%PATH% and retry the build process.

Thanks to Clive Bluston for posting the information in the Borland forum, and to Fedder Skovgaard for giving me the link to the newsgroup archive.

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