On 11/18/14 0:38, Joseph Myers wrote: > On Sat, 15 Nov 2014, Chen Gang wrote: > >> Also in c_common_read_pch(), when failure occurs, also need be sure the >> 'fd' is not '-1' for the next close operation. > > Please clarify how c_common_read_pch gets called with fd == -1. > Certainly checking after an error is too late; we shouldn't call fdopen in > that case at all, and I think something further up the call chain should > have avoided calling c_common_read_pch with fd == -1 at all (the question > is just exactly what point on the call chain is missing such a check and > needs it added). >
According to current source code, the author wants 'fd' should never be '-1' in c_common_read_pch(). "grep -rn read_pch *" in root directory, then "grep -rn _cpp_stack_file *", can know it is used in 3 areas: - c_common_pch_pragma() in "gcc/c-family/c-pch.c", it has already checked 'fd' before call c_common_read_pch() - _cpp_stack_include() in "libcpp/files.c", before _cpp_stack_file(), has called and checked _cpp_find_file(). - cpp_read_main_file() in "libcpp/init.c", before _cpp_stack_file(), has called and checked _cpp_find_file(). In c_common_read_pch(), even if 'fd' is '-1', we should check it firstly before call fdopen(), instead of check '-1' in failure code block. But for me, it contents another 2 related issues: - _cpp_find_file() always return a valid pointer, so related check code "file == NULL" is no use for _cpp_find_file() in _cpp_stack_include(). - According to its comments, _cpp_find_file() can not be sure of 'file->fd' must not be '-1', even when "file->err_no == 0", we need reopen it if necessary. Thanks. -- Chen Gang Open, share, and attitude like air, water, and life which God blessed
