283 lines
10 KiB
Text
283 lines
10 KiB
Text
Quick start documentation for the header file utilities.
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This isn't a full breakdown of the tools, just they typical use scenarios.
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- Each tool accepts -h to show it's usage. Usually no parameters will also
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trigger the help message. Help may specify additional functionality to what is
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listed here.
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- For all tools, option format for specifying filenames must have no spaces
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between the option and filename.
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ie.: tool -lfilename.h target.h
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- Many of the tools are required to be run from the core gcc source directory
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containing coretypes.h. Typically that is in gcc/gcc from a source checkout.
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For these tools to work on files not in this directory, their path needs to be
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specified on the command line.
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ie.: tool c/c-decl.cc lto/lto.cc
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- options can be intermixed with filenames anywhere on the command line
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ie. tool ssa.h rtl.h -a is equivalent to
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tool ssa.h -a rtl.h
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gcc-order-headers
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-----------------
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This will reorder any primary backend headers files known to the tool into a
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canonical order which will resolve any hidden dependencies they may have.
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Any unknown headers will simply be placed after the recognized files, and
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retain the same relative ordering they had.
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This tool must be run in the core gcc source directory.
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Simply execute the command listing any files you wish to process on the
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command line.
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Any files which are changed are output, and the original is saved with a
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.bak extention.
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ex.: gcc-order-headers tree-ssa.cc c/c-decl.cc
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-s will list all of the known headers in their canonical order. It does not
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show which of those headers include other headers, just the final canonical
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ordering.
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if any header files are included within a conditional code block, the tool
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will issue a message and not change the file. When this happens, you can
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manually inspect the file to determine if reordering it is actually OK. Then
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rerun the command with the -i option. This will ignore the conditional error
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condition and perform the re-ordering anyway.
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If any #include line has the beginning of a multi-line comment, it will also
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refuse to process the file until that is resolved by terminating the comment
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on the same line, or removing it.
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show-headers
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------------
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This will show the include structure for any given file. Each level of nesting
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is indented, and when any duplicate headers are seen, they have their
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duplicate number shown
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-i may be used to specify additional search directories for headers to parse.
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-s specifies headers to look for and emphasize in the output.
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This tool must be run in the core gcc source directory.
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ex.: show-headers -sansidecl.h tree-ssa.cc
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tree-ssa.cc
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config.h
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auto-host.h
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ansidecl.h (1) <<-------
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system.h
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safe-ctype.h
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filenames.h
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hashtab.h (1)
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ansidecl.h (2) <<-------
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libiberty.h
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ansidecl.h (3) <<-------
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hwint.h
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coretypes.h
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machmode.h (1)
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insn-modes.h (1)
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signop.h
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<...>
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count-headers
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-------------
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simply count all the headers found in the specified files. A summary is
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printed showing occurrences from high to low.
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ex.: count-headers tree*.c
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86 : coretypes.h
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86 : config.h
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86 : system.h
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86 : tree.h
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82 : backend.h
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80 : gimple.h
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72 : gimple-iterator.h
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70 : ssa.h
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68 : fold-const.h
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<...>
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included-by
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-----------
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This tool will search all the .c,.cc and .h files and output a list of files
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which include the specified header(s).
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A 4 level deep 'find' of all source files is performed from the current
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directory and each of those is inspected for a #include of the specified
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headers. So expect a little bit of slowness.
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-i limits the search to only other header files.
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-c limits the search to .c and .cc files.
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-a shows only source files which include all specified headers.
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-f allows you to specify a file which contains a list of source files to
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check rather than performing the much slower find command.
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ex: included-by tree-vectorizer.h
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config/aarch64/aarch64.cc
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config/i386/i386.cc
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config/rs6000/rs6000.cc
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tree-loop-distribution.cc
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tree-parloops.cc
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tree-ssa-loop-ivopts.cc
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tree-ssa-loop.cc
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replace-header
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--------------
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This tool simply replaces a single header file with one or more other headers.
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-r specifies the include to replace, and one or more -f options specify the
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replacement headers, in the order they occur.
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This is commonly used in conjunction with 'included-by' to change all
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occurrences of a header file to something else, or to insert new headers
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before or after.
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ex: to insert #include "before.h" before every occurence of tree.h in all
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.c and .cc source files:
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replace-header -rtree.h -fbefore.h -ftree.h `included-by -c tree.h`
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reduce-headers
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--------------
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This tool removes any header files which are not needed from a source file.
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This tool must be run for the core gcc source directory, and requires either
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a native build and sometimes target builds, depending on what you are trying
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to reduce.
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it is good practice to run 'gcc-order-headers' on a source file before trying
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to reduce it. This removes duplicates and performs some simplifications
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which reduce the chances of the reduction tool missing things.
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start with a completely bootstrapped native compiler.
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Any desired target builds should be built in one directory using a modified
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config-list.mk file which does not delete the build directory when it is done.
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any target directories which do not successfully complete a 'make all-gcc'
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may cause the tool to not reduce anything.
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(todo - provide a config-list.mk that leaves successful target builds, but
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deletes ones which do not compile)
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The tool will examine all the target builds to determine which targets build
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the file, and include those targets in the testing.
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The tool will analyze a source file and attempt to remove each non-conditional
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header from last to first in the file.:
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It will first attempt to build the native all-gcc target.
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If that succeeds, it will attempt to build any target build .o files
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If that succeeds, it will check to see if there are any conditional
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compilation dependencies between this header file and the source file or
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any header which have already been determined as non-removable.
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If all these tests are passed, the header file is determined to be removable
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and is removed from the source file.
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This continues until all headers have been checked.
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At this point, a bootstrap is attempted in the native build, and if that
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passes the file is considered reduced.
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Any files from the config subdirectory require target builds to be present
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in order to proceed.
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A small subset of targets has been determined to provide excellent coverage,
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at least as of Aug 31/15 . They were found by reducing all the files
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contained in libbackend.a oer a full set of targets(207). All conditions
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which disallowed removal of a header file were triggered by one or more of
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these targets. They are also known to the tool. When building targets it
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will check those targets before the rest.
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This coverage can be achieved by building config-list.mk with :
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LIST="aarch64-linux-gnu arm-netbsdelf c6x-elf epiphany-elf hppa2.0-hpux10.1 i686-mingw32crt i686-pc-msdosdjgpp mipsel-elf powerpc-eabisimaltivec rs6000-ibm-aix5.1.0 sh-superh-elf sparc64-elf"
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-b specifies the native bootstrapped build root directory
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-t specifies a target build root directory that config-list.mk was run from
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-f is used to limit the headers for consideration.
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example:
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mkdir gcc // checkout gcc in subdir gcc
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mdsir build // boostrap gcc in subdir build
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mkdir target // create target directory and run config-list.mk
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cd gcc/gcc
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reduce-headers -b../../build -t../../targets -falias.h -fexpr.h tree*.c (1)
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# This will attempt to remove only alias.h and expr.h from tree*.c
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reduce-headers -b../../build -t../../targets tree-ssa-live.cc
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# This will attempt to remove all header files from tree-ssa-live.cc
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the tool will generate a number of log files:
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reduce-headers.log : All compilation failures from attempted reductions.
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reduce-headers.sum : One line summary of what happened to each source file.
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(All the remaining logs are appended to, so if the tool is run multiple times
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these files are just added to. You must physically remove them yourself in
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order to reset the logs.)
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reduce-headers-kept.log: List of all the successful compiles that were
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ignored because of conditional macro dependencies
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and why it thinks that is the case
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$src.c.log : for each failed header removal, the compilation
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messages as to why it failed.
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$header.h.log: The same log is put into the relevant header log as well.
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a sample output from ira.cc.log:
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Compilation failed:
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for shrink-wrap.h:
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============================================
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/gcc/2015-09-09/gcc/gcc/ira.cc: In function ‘bool split_live_ranges_for_shrink_wrap()’:
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/gcc/2015-09-09/gcc/gcc/ira.cc:4839:8: error: ‘SHRINK_WRAPPING_ENABLED’ was not declared in this scope
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if (!SHRINK_WRAPPING_ENABLED)
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^
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make: *** [ira.o] Error 1
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the same message would be put into shrink-wrap.h.log.
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graph-header-logs
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-----------------
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This tool will parse all the messages from the .C files, looking for failures
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that show up in other headers... meaning there is a compilation dependency
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between the 2 header files.
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The tool will aggregate all these and generate a graph of the dependencies
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exposed during compilation. Red lines indicate dependencies that are
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present because a header file physically includes another file. Black lines
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represent data dependencies causing compilation failures if the header is
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not present.
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ex.: graph-header-logs *.c.log
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graph-include-web
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-----------------
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This tool can be used to visualize the include structure in files. It is
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rapidly turned useless if you specify too many things, but it can be
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useful for finding cycles and redundancies, or simply to see what a single
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file looks like.
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ex.: graph-include-web tree.cc
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