Fortran compiler flags correspondence

Compiler vendors checked here

• gfortran: Fortran compiler for the GCC project.
• ifort: Intel’s classical Fortran compiler.
• ifx: Intel’s new Fortran compiler based on LLVM.

List of selected flags

Usage	gfortran	ifort	ifx
Inter-procedure optimization	-flto	-ip	-ipo
Backtrace generation	-fbacktrace	-traceback	as ifort
Check out-of-bounds	-fcheck=bounds	-check bounds	as ifort
Check uninitialized variables	-Wuninitialized1	-check uninit	as ifort
Check pointer issues	-fcheck=pointer	-check pointers	as ifort
Use single byte as record length unit	n/a2	-assume byterecl	as ifort
Adhere to value-safe optimizations for f.p. computations	-fno-fast-math	-fp-model precise	as ifort
Enable stack overflow security checks	as ifort	-fstack-protector	as ifort
Enable overflow/divide-by-zero/invalid f.p. exceptions	-ffpe-trap=invalid,zero,overflow	-fpe0	as ifort
Implicit initialization to signaling NaN	-finit-real=snan3	-init=snan	as ifort
Control whether to implicitly initialize arrays	n/a	-init=arrays4	as ifort

Remarks

When compiling FHI-aims with mpiifx, a segmentation fault happens during the compilation of elpa_impl.f90 in ELPA with -ipo switched on. In a thread about ifort in the Intel forum, Jim Dempsey pointed out that this can happen for large project. It is also discussed in the Fortran Discourse.

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1. It warns instead of quit with error. Implicitly switched on with -fcheck=all. ↩︎

2. gfortran always uses 1 byte as record length unit. ifort/ifx uses 4-byte unit by default unless -assume byterecl is specified. ↩︎

3. It also applies to real and imaginary parts of complex type. ↩︎

4. Must work with -init=snan or -init=zero to specify the initial value. ↩︎