http://gcc.gnu.org/bugzilla/show_bug.cgi?id=54736
--- Comment #5 from Shane Hart <shart6 at utk dot edu> 2012-09-30 20:56:39 UTC --- (In reply to comment #4) > Am 30.09.2012 21:12, schrieb shart6 at utk dot edu: > > If n_elist = 1, then high = low = 0, and the funtion will always return 0, > > even > > if the unit passed in to search for is in the exception list. > > If there are n_elist exceptions, then they can be found in > elist[0], ..., elist[n_elist-1]. > > If there is one exception, then it can be found at elist[0]. That is true, but the function will not return 1 (true, a match was found in elist) when there is only one exception stored. It will skip over the while loop, set *ip to 0, and return 0 (false, the exception was not found!). This can be illustrated: 1) Call the program, setting only one exception (in this case unit 21): [shane@shane-laptop ~/temp/testgfortran]$ GFORTRAN_CONVERT_UNIT='native;big_endian:21' gnu_wrap gdb ./test_read 2) Set a break point at where the library enquires as to the endianness of the file to be opened: Breakpoint 1, _gfortrani_get_unformatted_convert (unit=21) at ../../../libgfortran/runtime/environ.c:848 3) We will step into search_unit (with unit = 21). Everything is great. however, since n_elist = 1, high = low = 0, and the while loop is skipped over: (gdb) step 471 while (high - low > 1) (gdb) step 485 if (unit > elist[high].unit) 4) And 0 is returned (unit exception not found!) (gdb) step 490 return 0; 5) The library is told to open unit 21 (which is in the exception list at 0) as default endianness: _gfortrani_get_unformatted_convert (unit=21) at ../../../libgfortran/runtime/environ.c:856 856 return def;
