What is xlc-wrapper

This is intended to fix compiler parameters position incompatibility that happens due to use of configure scripts and makefiles written for unix-like systems where gcc is default compiler. So this tool used to minimize changes to be done to configuration scripts and makefiles.

xlc-wrapper provides a miniature compatibility layer, intended to resolve recurrent problems that arise due to inconvenient standard library-level functionality. At the moment it only contains the following:

• A fix for malloc and co. that translates calls to malloc(0) to calls to malloc(1). See compatmalloc.c for more details.

These are not intended to be permanant fixes. The proper way to fix these problems would be to modify the programs exhibiting them to be more portable. However, there are many packages, and we have only so much time that we can spend applying the same fix over and over again.

Usage

make
make test
# installs the library, config file, and stdlib.h
# It installs to $CONDA_PREFIX, xlc-wrapper will expect it to be there
make install

The config file takes care of everything except the library search path, since apparently -L is not valid in a configuration file. The easiest way to fix this is to set _C89_LIBDIRS to something like "$CONDA_PREFIX/unixcompat /lib /usr/lib". You would also need to set _CXX_LIBDIRS for C++.

The dynamic version does not work with the current setup, so unixcompat will always be linked statically. Fortunately it is quite small.

make uninstall will remove everything that was installed.

Permanent Solutions

There are a few ways to make non-compliant programs "correct". The best long-term solutions all involve changes at potentially every call site in the program. An ongoing list of potential approaches follow.

1. Change each subsequent result != NULL check to also check for whether size == 0. These are the areas that have actually caused problems. Basically, change this:

ptr = malloc(size);
if (!ptr) {
  /* error stuff */

to this:

ptr = malloc(size);
if (!ptr && size != 0) {
  /* error stuff */

• This should not break the target programs if they actually work on other platforms. Dereferencing malloc(0) pointers will crash on most platforms (I think?), so presumably, if the program works, whenever it gets a pointer from malloc(0), it doesn't use it.

Authors

Rick Harris - xlc-wrapper base

Giancarlo Frix - malloc compatibility layer

Mikhail Sviridov - support and refactoring

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