Re: Misc fixes

Andy, in plain C the result of a cast is never an lvalue. It's a gcc extension. Compilation fails with plain old ordinary ANSI C compilers. I will undo this part of the patch, because it breaks actual observed C compiler failure. Again, I'm not suggesting this is the best solution, but it allows compilation for now. Index: src/glyphs-x.h =================================================================== RCS file: /usr/CVSroot/XEmacs/xemacs/src/glyphs-x.h,v retrieving revision 1.4.2.8 diff -u -r1.4.2.8 glyphs-x.h --- src/glyphs-x.h 2000/02/13 00:26:22 1.4.2.8 +++ src/glyphs-x.h 2000/02/13 20:18:32 ＠＠ -137,9 +137,9 ＠＠ #define XIMAGE_INSTANCE_X_CLIPWINDOW(i) \ IMAGE_INSTANCE_X_CLIPWINDOW (XIMAGE_INSTANCE (i)) #define IMAGE_INSTANCE_X_SUBWINDOW_ID(i) \ - (* (Window *) & IMAGE_INSTANCE_SUBWINDOW_ID (i)) + ((Window)IMAGE_INSTANCE_SUBWINDOW_ID (i)) #define IMAGE_INSTANCE_X_WIDGET_ID(i) \ - ( * (Widget *) & IMAGE_INSTANCE_SUBWINDOW_ID (i)) + ((Widget)IMAGE_INSTANCE_SUBWINDOW_ID (i)) #endif /* HAVE_X_WINDOWS */ #endif /* INCLUDED_glyphs_x_h_ */ A cast is a valid lvalue if its operand is an lvalue. A simple assignment whose left-hand side is a cast works by converting the right-hand side first to the specified type, then to the type of the inner left-hand side expression. After this is stored, the value is converted back to the specified type to become the value of the assignment. Thus, if `a' has type `char *', the following two expressions are equivalent: (int)a = 5 (int)(a = (char *)(int)5) An assignment-with-arithmetic operation such as `+=' applied to a cast performs the arithmetic using the type resulting from the cast, and then continues as in the previous case. Therefore, these two expressions are equivalent: (int)a += 5 (int)(a = (char *)(int) ((int)a + 5)) You cannot take the address of an lvalue cast, because the use of its address would not work out coherently. Suppose that `&(int)f' were permitted, where `f' has type `float'. Then the following statement would try to store an integer bit-pattern where a floating point number belongs: *&(int)f = 1; This is quite different from what `(int)f = 1' would do--that would convert 1 to floating point and store it. Rather than cause this inconsistency, we think it is better to prohibit use of `&' on a cast. If you really do want an `int *' pointer with the address of `f', you can simply write `(int *)&f'.