Setting the environment variable LDR_CNTRL is discouraged.  It is much better to set the value in the executable header. Best to set it at link time, but one can use ldedit.

The issue with the segments in 32 bit mode is a trade off between heap memory and shmat attached shared memory. If one wanted to use Python with some forms of shared memory, one cannot allocate all of the segments to heap. Setting maxdata too large can cause unexpected failures if shared memory is used.

Increasing the default maxdata value seems like a good idea. The default GCC for AIX builds with a larger value. But it adds the command to LDFLAGS, which is applied everywhere, but not a significant problem and cc1* do not use shared memory.

One subtlety with LDFLAG is XLC wants the flag directly (-bmaxdata:0x40000000) but GCC needs to use -Wl,-bmaxdata.