1<!--===- docs/RuntimeEnvironment.md 2 3 Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. 4 See https://llvm.org/LICENSE.txt for license information. 5 SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception 6 7--> 8 9```{contents} 10--- 11local: 12--- 13``` 14 15# Environment variables of significance to Fortran execution 16 17A few environment variables are queried by the Fortran runtime support 18library. 19 20The following environment variables can affect the behavior of 21Fortran programs during execution. 22 23## `DEFAULT_UTF8=1` 24 25Set `DEFAULT_UTF8` to cause formatted external input to assume UTF-8 26encoding on input and use UTF-8 encoding on formatted external output. 27 28## `FORT_CONVERT` 29 30Determines data conversions applied to unformatted I/O. 31 32* `NATIVE`: no conversions (default) 33* `LITTLE_ENDIAN`: assume input is little-endian; emit little-endian output 34* `BIG_ENDIAN`: assume input is big-endian; emit big-endian output 35* `SWAP`: reverse endianness (always convert) 36 37## `FORT_CHECK_POINTER_DEALLOCATION` 38 39Fortran requires that a pointer that appears in a `DEALLOCATE` statement 40must have been allocated in an `ALLOCATE` statement with the same declared 41type. 42The runtime support library validates this requirement by checking the 43size of the allocated data, and will fail with an error message if 44the deallocated pointer is not valid. 45Set `FORT_CHECK_POINTER_DEALLOCATION=0` to disable this check. 46 47## `FORT_FMT_RECL` 48 49Set to an integer value to specify the record length for list-directed 50and `NAMELIST` output. 51The default is 72. 52 53## `NO_STOP_MESSAGE` 54 55Set `NO_STOP_MESSAGE=1` to disable the extra information about 56IEEE floating-point exception flags that the Fortran language 57standard requires for `STOP` and `ERROR STOP` statements. 58