Variable length array allocation in polyhedron.c is not supported on all platforms

[g5t]

Allocating arrays with sizes determined by the value of a struct member, as in,

McCode/mcstas-comps/share/polyhedron.c

Lines 661 to 666 in bdd87f6

	double dtime[a->nf];
	Coords dpoint[a->nf];
	double time[a->nf];
	Coords point[a->nf];
	int plane_number[a->nf];
	int type[a->nf];

fails under Microsoft's C/C++ Optimizing Compiler Version 19.42.34435 for x64

E  cl.exe /DWIN32 /D_WINDOWS /Zi /O2 /Ob1 /DNDEBUG g\source.c /W0 /link /out:"g\source.exe"
E  failed with output
E  source.c
E  g\source.c(8491): error C2057: expected constant expression
E  g\source.c(8491): error C2466: cannot allocate an array of constant size 0
E  g\source.c(8491): error C2133: 'dtime': unknown size
E  g\source.c(8492): error C2057: expected constant expression
E  g\source.c(8492): error C2466: cannot allocate an array of constant size 0
E  g\source.c(8492): error C2133: 'dpoint': unknown size
E  g\source.c(8493): error C2057: expected constant expression
E  g\source.c(8493): error C2466: cannot allocate an array of constant size 0
E  g\source.c(8493): error C2133: 'time': unknown size
E  g\source.c(8494): error C2057: expected constant expression
E  g\source.c(8494): error C2466: cannot allocate an array of constant size 0
E  g\source.c(8494): error C2133: 'point': unknown size
E  g\source.c(8495): error C2057: expected constant expression
E  g\source.c(8495): error C2466: cannot allocate an array of constant size 0
E  g\source.c(8495): error C2133: 'plane_number': unknown size
E  g\source.c(8496): error C2057: expected constant expression
E  g\source.c(8496): error C2466: cannot allocate an array of constant size 0
E  g\source.c(8496): error C2133: 'type': unknown size

This method of variable length array allocation would appear to be part of the C99 standard, but according to Microsoft

The compiler doesn't implement several required features of C99, so it isn't possible to specify C99 conformance, either.

Trying either of the supported language specifications, /std:c11 or /std:c17 does not allow an instrument using the polyhedron intersection code to compile for this tested version of the Microsoft C compiler.

Replacing this construction with paired allocation and freeing memory should be more cross-platform friendly.

[g5t]

This same construction appears elsewhere. Notably in supermirror-lib.c

McCode/mcstas-comps/share/supermirror-lib.c

Line 1949 in bdd87f6

int n_skip_plane = 2; int skip_plane[n_skip_plane];

[willend]

@g5t thanks for giving a hand with this.

I corrected many such static allocation syntaxes for the "initial windows conda support", but have apparently overlooked these.