Re: [PATCH][RFC] Immediate compiler exit on missing header file

[Richard Guenther <richard dot guenther at gmail dot com>]

On Sun, Mar 29, 2009 at 12:50 PM, Simon Baldwin <simonb@google.com> wrote:
> This patch is an attempt to provide a simple way for gcc to exit immediately
> when it runs across a missing header file. ?At present, gcc tries to continue
> with compilation. ?Where a header is missing, the cascade of follow on errors
> often obscures the initial cause.
>
> Though the patch works, and is short, I'm not entirely thrilled about it,
> and would welcome ideas for improvement or rewrite:
>
> ?- Returning only EOF from the lexer on error to unwind the parser stack
> ? ?looks a bit flimsy. ?Long jump out or exit() both seemed worse, though.
> ?- The -W... flag does not work with -Wno-error=, because cpplib does not
> ? ?use gcc's diagnostic machinery, but rather its own. ?I couldn't see a
> ? ?ready way round that. ?Perhaps just a flag that isn't attached to -W?
>
> Thanks for any ideas or feedback.

Hm, we have -Wfatal-errors to stop after the first error.  Does this work for
missing headerfile errors?  If so, can we name the new flag like
-Wfatal-header-errors or something like that?  -Wmissing-header-file
doesn't suggest that it would stop but instead only warn.

Richard.

>
> gcc/ChangeLog
> 2009-03-29 ?Simon Baldwin ?<simonb@google.com>
>
> ? ? ? ?* c.opt (Wmissing-header-file): New flag.
> ? ? ? ?* c-opts.c (c_common_handle_option): Handle new flag.
> ? ? ? ?* doc/invoke.texi (Warning Options): Documented -Wmissing-header-file.
>
> libcpp/ChangeLog
> 2009-03-29 ?Simon Baldwin ?<simonb@google.com>
>
> ? ? ? ?* internal.h (cpp_reader): Add return_only_eof flag.
> ? ? ? ?* files.c (_cpp_find_file): Set return_only_eof on missing header.
> ? ? ? ?* include/cpplib.h (cpp_options): Add new structure flag
> ? ? ? ?eofs_on_missing_include_files.
> ? ? ? ?* lex.c (_cpp_lex_token): Convert all return tokens to EOF if
> ? ? ? ?return_only_eof.
>
>
> Index: gcc/doc/invoke.texi
> ===================================================================
> --- gcc/doc/invoke.texi (revision 145225)
> +++ gcc/doc/invoke.texi (working copy)
> @@ -244,7 +244,7 @@ Objective-C and Objective-C++ Dialects}.
> ?-Winvalid-pch -Wlarger-than=@var{len} ?-Wunsafe-loop-optimizations @gol
> ?-Wlogical-op -Wlong-long @gol
> ?-Wmain ?-Wmissing-braces ?-Wmissing-field-initializers @gol
> --Wmissing-format-attribute ?-Wmissing-include-dirs @gol
> +-Wmissing-format-attribute ?-Wmissing-header-file ?-Wmissing-include-dirs @gol
> ?-Wmissing-noreturn ?-Wno-mudflap @gol
> ?-Wno-multichar ?-Wnonnull ?-Wno-overflow @gol
> ?-Woverlength-strings ?-Wpacked ?-Wpacked-bitfield-compat ?-Wpadded @gol
> @@ -3010,6 +3010,11 @@ int b[2][2] = @{ @{ 0, 1 @}, @{ 2, 3 @}
>
> ?This warning is enabled by @option{-Wall}.
>
> +@item -Wmissing-header-file @r{(C, C++, Objective-C and Objective-C++ only)}
> +@opindex Wmissing-header-file
> +@opindex Wno-missing-header-file
> +Stop compilation with an error on missing include file.
> +
> ?@item -Wmissing-include-dirs @r{(C, C++, Objective-C and Objective-C++ only)}
> ?@opindex Wmissing-include-dirs
> ?@opindex Wno-missing-include-dirs
> Index: gcc/c.opt
> ===================================================================
> --- gcc/c.opt ? (revision 145225)
> +++ gcc/c.opt ? (working copy)
> @@ -308,6 +308,10 @@ Wmissing-format-attribute
> ?C ObjC C++ ObjC++ Var(warn_missing_format_attribute) Warning
> ?Warn about functions which might be candidates for format attributes
>
> +Wmissing-header-file
> +C ObjC C++ ObjC++ Warning
> +Stop compilation with an error on missing include file
> +
> ?Wmissing-include-dirs
> ?C ObjC C++ ObjC++ Warning
> ?Warn about user-specified include directories that do not exist
> Index: gcc/c-opts.c
> ===================================================================
> --- gcc/c-opts.c ? ? ? ?(revision 145225)
> +++ gcc/c-opts.c ? ? ? ?(working copy)
> @@ -454,6 +454,10 @@ c_common_handle_option (size_t scode, co
> ? ? ? enable_warning_as_error ("implicit-function-declaration", value, CL_C | CL_ObjC);
> ? ? ? break;
>
> + ? ?case OPT_Wmissing_header_file:
> + ? ? ?cpp_opts->eofs_on_missing_include_files = value;
> + ? ? ?break;
> +
> ? ? case OPT_Wformat:
> ? ? ? set_Wformat (value);
> ? ? ? break;
> Index: libcpp/files.c
> ===================================================================
> --- libcpp/files.c ? ? ?(revision 145225)
> +++ libcpp/files.c ? ? ?(working copy)
> @@ -497,6 +497,10 @@ _cpp_find_file (cpp_reader *pfile, const
> ? ? ? ? ? ? ? ?cpp_error (pfile, CPP_DL_ERROR,
> ? ? ? ? ? ? ? ? ? ? ? ? ? "use -Winvalid-pch for more information");
> ? ? ? ? ? ?}
> +
> + ? ? ? ? /* If requested, only return a stream of EOFs from now on. ?*/
> + ? ? ? ? if (CPP_OPTION (pfile, eofs_on_missing_include_files))
> + ? ? ? ? ? pfile->return_only_eof = 1;
> ? ? ? ? ?break;
> ? ? ? ?}
>
> Index: libcpp/include/cpplib.h
> ===================================================================
> --- libcpp/include/cpplib.h ? ? (revision 145225)
> +++ libcpp/include/cpplib.h ? ? (working copy)
> @@ -321,6 +321,10 @@ struct cpp_options
> ? /* Nonzero means warn if slash-star appears in a comment. ?*/
> ? unsigned char warn_comments;
>
> + ?/* Nonzero means return a stream of eof's if an include file does not
> + ? ? exist. ?*/
> + ?unsigned char eofs_on_missing_include_files;
> +
> ? /* Nonzero means warn if a user-supplied include directory does not
> ? ? ?exist. ?*/
> ? unsigned char warn_missing_include_dirs;
> Index: libcpp/internal.h
> ===================================================================
> --- libcpp/internal.h ? (revision 145225)
> +++ libcpp/internal.h ? (working copy)
> @@ -391,6 +391,10 @@ struct cpp_reader
> ? /* Error counter for exit code. ?*/
> ? unsigned int errors;
>
> + ?/* Flag to force only EOF token returns, used to coerce the lexer into
> + ? ? a hard error state. ?*/
> + ?unsigned int return_only_eof : 1;
> +
> ? /* Buffer to hold macro definition string. ?*/
> ? unsigned char *macro_buffer;
> ? unsigned int macro_buffer_len;
> Index: libcpp/lex.c
> ===================================================================
> --- libcpp/lex.c ? ? ? ?(revision 145225)
> +++ libcpp/lex.c ? ? ? ?(working copy)
> @@ -944,6 +944,10 @@ _cpp_lex_token (cpp_reader *pfile)
> ? ? ? ?break;
> ? ? }
>
> + ?/* Convert all returned tokens to EOF if failing on error. ?*/
> + ?if (pfile->return_only_eof)
> + ? ?result->type = CPP_EOF;
> +
> ? return result;
> ?}
>
>