Ross Paterson
On Tue, Feb 02, 2010 at 03:51:18PM +0100, Jose A. Ortega Ruiz wrote:
[...] The problem is that the size and some of the offsets of the C struct statfs computed by hsc2c are wrong: i'm in a 32bit linux system, and i've checked, using a C program, that sizeof(struct statfs) is 64 (hsc2 is giving 84 -- although perhaps Haskell needs additional space for housekeeping?), and that the offsets of f_bfree and f_bavail are, respectively, 12 and 16 (not 16 and 24). Also, i know that 12 and 16 are the right values because putting them by hand gives me the correct statfs values.
If you compile your C program with -D_FILE_OFFSET_BITS=64 you'll get the same numbers that hsc2hs does.
But when i use those offsets (16, 24) in my Haskell program (generated by hsc2hs), i get the wrong values when i inspect the struct filled by statfs() (via the call performed by Haskell's FFI), while if i put (by hand this time) the ones (12, 16) given by the C program without _FILE_OFFSET_BITS defined, the results are correct. So it looks like the C library, or the generated code, is not using that value for _FILE_OFFSET_BITS. Do i need to compile my Haskell code using a similar flag? (Sorry if i'm missing something obvious.) Thanks! jao