Is there a limit to the number of arguments passed

Question

I came across some Fortran 90 code where 68 arguments are passed to a function. Upon searching the web I only found something about a limit of passing 256 bytes for some CUDA Fortran related stuff (http://www.pgroup.com/userforum/viewtopic.php?t=2235&sid=f241ca3fd406ef89d0ba08a361acd962).

So I wonder: is there a limit to the number of arguments that may be passed to a function for Intel/Visual/GNU fortran compilers?

Answer 1

I don't believe that the Fortran standards explicitly impose such a limit. However, they do place a limit on the length of a line of code (132 characters) and the number of lines which can together form a single statement (256). I'll leave it to you to figure out how many arguments you could use in a single call to a routine.

Many compilers on the market have more relaxed limits on both statement length and the number of continuation lines that can be used. However, it would not surprise me if a compiler did impose a maximum number of arguments for any routine but the number is probably higher than any realistic need requires.

Answer 2

I came across this discussion of the Fortran 90 standards:

http://www.nag.co.uk/sc22wg5/Guidelines_for_Bindings-b.html

The relevant section is in italics below:

3.4 Statements

Constraints on the length of a Fortran statement impose an upper limit on the length of a procedure call. Although it is unlikely to be a serious imposition, a single Fortran statement in free-form format is subject to an upper limit of 5241 characters, including a possible label (F90 sections 3.3.1, 3.3.1.4); in fixed-form format the upper limit is 1320 characters plus a possible label (F90 section 3.3.2). These limits are subject to the characters being of "default kind", that is in practice single-byte characters; for double-byte characters, used for example for ideographic languages, the limits are processor-dependent but are likely to be of the same order of size.

There is no limit in the Fortran Standard on the maximum number of arguments to a procedure.

I have a security tool that I am developing in my research that analyzes binaries. I knew that the C language has limits on number of arguments (31 in the C90 standard, 127 in the C99 standard), so I thought that I could dimension a vector to hold 128 items pertaining to incoming arguments. I encountered a FORTRAN-derived binary that had 290 arguments passed, which led me to this discussion. The binary is from the SPEC CPU2006 benchmark suite, benchmark 481.wrf, where I see a procedure that is named (in the binary) "solve_interface_" which sets up 290 arguments on the stack and then calls "solve_em_" which actually processes these arguments. You can no doubt find the FORTRAN source code for these procedures online. The binary was produced by the GNU compiler tools for an x86/Linux/ELF system.