https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120131
--- Comment #6 from kargls at comcast dot net --- (In reply to Vladimir Terzi from comment #5) > After a fruitful discussion in Stack Overflow, I understand that the model > set of integers in Fortran is symmetric about zero according to the formula > in section 16.4 of https://j3-fortran.org/doc/year/24/24-007.pdf , and, > therefore, `gfortran` may reject the literal -2147483648 (although it is > inconvenient and there are no technical reasons to reject it). But it was > already known in 2006 that this change will cause "bogus bug reports" (like > written in https://gcc.gnu.org/legacy-ml/fortran/2006-09/msg00008.html) and > there are already multiple of such reports on this site. Then why wasn't > the error message clarified? The original error message was % gfortran14 -o z a.f90 a.f90:1:21: 1 | print *, -2147483648 | 1 Error: Integer too big for its kind at (1). Then this commit happen. 2007-08-09 Tobias Burnus <bur...@net-b.de> PR fortran/33001 * arith.c (arith_error): Point in the error message to -fno-range-check. which gives (with courtesy wrap of a long line) % gfortran14 -o z a.f90 a.f90:1:21: 1 | print *, -2147483648 | 1 Error: Integer too big for its kind at (1). This check can be disabled with the option '-fno-range-check' Then this commit happen 2007-11-29 Steven G. Kargl <kar...@comcast.net> PR fortran/34230 * fortran/arith.c (gfc_check_real_range): Set intermediate values to +-Inf and 0 when -fno-range-check is in effect. * fortran/invoke.texi: Improve -fno-range-check description. I suppose it is somewhat naive of gfortran contributors to expect that users read the documentation supplied with the compiler. ‘-fno-range-check’ Disable range checking on results of simplification of constant expressions during compilation. For example, GNU Fortran gives an error at compile time when simplifying ‘a = 1. / 0’. With this option, no error is given and ‘a’ is assigned the value ‘+Infinity’. If an expression evaluates to a value outside of the relevant range of [‘-HUGE()’:‘HUGE()’], then the expression is replaced by ‘-Inf’ or ‘+Inf’ as appropriate. Similarly, ‘DATA i/Z'FFFFFFFF'/’ results in an integer overflow on most systems, but with ‘-fno-range-check’ the value "wraps around" and ‘i’ is initialized to -1 instead. Those last two sentences are important. Consider the simple example, % cat b.f90 print *, 1 + -1 end % gfortran14 -o z b.f90 && ./z b.f90:1:15: 1 | print *, 1 + -1 | 1 Warning: Extension: Unary operator following arithmetic operator (use parentheses) at (1) 0 % ~/tmp/root/build/bin/flang -o z b.f90 && ./z 0 gfortran gives a warning while flang does not; but, it can be forced to tell you that the program is invalid % ~/tmp/root/build/bin/flang -o z -pedantic b.f90 && ./z ./b.f90:1:14: portability: nonstandard usage: signed mult-operand print *, 1 + -1 ^^ % ~/lfortran/work/bin/lfortran -o z b.f90 % ./z 0 There appears to be no option with lfortran to diagnose the invalid code. Now, returning to a.f90 above. gfortran14 -o z a.f90 && ./z a.f90:1:21: 1 | print *, -2147483648 | 1 Error: Integer too big for its kind at (1). This check can be disabled with the option '-fno-range-check' % gfortran14 -o z -fno-range-check a.f90 && ./z -2147483648 % gfortran14 -o z -fno-range-check -pedantic a.f90 && ./z a.f90:1:21: 1 | print *, -2147483648 | 1 Warning: Integer outside symmetric range implied by Standard Fortran at (1) -2147483648 So, yes, more than one gfortran contributor has thought about the corner case of -huge(1) - 1.
