On Thursday 12 of July 2012, Joel Rosdahl wrote: > On 6 July 2012 19:09, Lubos Lunak <[email protected]> wrote: > > the attached patches modify ccache to also support Clang PCH in addition > > to GCC PCH. > > Thanks! > > Regarding 0002-hash-clang-s-.pch-file-explicitly.patch: Why is the third > assignment of pch_file done outside the "if (stat(pchpath, &st) == 0)" > block? This means that pch_file and included_pch_file can be set even when > there is no .pch file, so remember_include_file will fail to stat the file > and then turn off the direct mode. The test suite also fails after the > patch, but passes if the pch_file assignment is moved into the block.
Right. I guess that was an oversight when I moved the "Multiple precompiled headers used" error to one place. Fixed version attached. > The patches look good otherwise. > > > PS: Since I've noticed in the archives the recent mail about issues with > > ccache and warnings about unused arguments: The proper way to use ccache > > with Clang is to set CCACHE_CPP2, which not only avoids these warnings, > > but in general Clang works suboptimally if passed preprocessed output > > (warning/error messages quoting sources are affected, some warnings are > > not supressed in headers). > > Do you have any idea about the performance impact of using CCACHE_CPP2 for > clang? Debug build of LibreOffice, warm disk caches, empty ccache, make -j4 in xmloff module: CCACHE_CPP2=1: 494.64user 34.99system 2:15.60elapsed 390%CPU (0avgtext+0avgdata 1309824maxresident)k 0inputs+3752560outputs (507major+13592550minor)pagefaults 0swaps not set: 457.17user 28.94system 2:06.15elapsed 385%CPU (0avgtext+0avgdata 1309312maxresident)k 0inputs+3758600outputs (444major+12098612minor)pagefaults 0swaps So in this case CCACHE_CPP2 adds about 8% overhead. It might make a difference for somebody, but I myself would prefer to get better error messages from Clang (and I actually use ccache only for a buildbot, so I don't find this worth the effort). If somebody would feel like playing with this, note that Clang 3.2 will have -E -Wp,-rewrite-includes, which only processes #include directives and nothing more (I wrote the feature to solve a similar problem when using Clang with Icecream for distributed builds, and I assume this is the only thing ccache in fact wants from -E too). So using this in ccache for Clang should presumably reduce this overhead. -- Lubos Lunak [email protected]
From d897f0388b35ca0b8e333e7e8edbd57a0c4ba3e1 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Lubo=C5=A1=20Lu=C5=88=C3=A1k?= <[email protected]> Date: Fri, 6 Jul 2012 18:45:05 +0200 Subject: [PATCH 2/2] hash clang's .pch file explicitly It does not appear anywhere in the preprocessed output, so process_preprocessed_file() would miss it. --- ccache.c | 31 +++++++++++++++++++++++++++++++ 1 files changed, 31 insertions(+), 0 deletions(-) diff --git a/ccache.c b/ccache.c index 12b62a4..926d6b2 100644 --- a/ccache.c +++ b/ccache.c @@ -171,6 +171,11 @@ static bool profile_generate = false; */ static bool using_precompiled_header = false; +/* + * The .gch/.pch file used for compilation. + */ +static char *included_pch_file = NULL; + /* How long (in microseconds) to wait before breaking a stale lock. */ unsigned lock_staleness_limit = 2000000; @@ -532,6 +537,16 @@ process_preprocessed_file(struct mdfour *hash, const char *path) hash_buffer(hash, p, (end - p)); free(data); + + /* Explicitly check the .gch/.pch file, Clang does not include any mention of it + in the preprocessed output. */ + if (included_pch_file) { + char *path = x_strdup(included_pch_file); + path = make_relative_path(path); + hash_string(hash, path); + remember_include_file(path, strlen(included_pch_file), hash); + } + return true; } @@ -1680,6 +1695,7 @@ cc_process_args(struct args *orig_args, struct args **preprocessor_args, */ if (compopt_takes_path(argv[i])) { char *relpath; + char *pch_file = NULL; if (i == argc-1) { cc_log("Missing argument to %s", argv[i]); stats_update(STATS_ARGS); @@ -1696,23 +1712,37 @@ cc_process_args(struct args *orig_args, struct args **preprocessor_args, if (stat(argv[i+1], &st) == 0) { cc_log("Detected use of precompiled header: %s", argv[i+1]); found_pch = true; + pch_file = x_strdup(argv[i+1]); } } else { char* gchpath = format("%s.gch", argv[i+1]); if (stat(gchpath, &st) == 0) { cc_log("Detected use of precompiled header: %s", gchpath); found_pch = true; + pch_file = x_strdup(gchpath); } else { char* pchpath = format("%s.pch", argv[i+1]); if (stat(pchpath, &st) == 0) { cc_log("Detected use of precompiled header: %s", pchpath); found_pch = true; + pch_file = x_strdup(pchpath); } free(pchpath); } free(gchpath); } + if (pch_file) { + if (included_pch_file) { + cc_log("Multiple precompiled headers used: %s and %s\n", + included_pch_file, pch_file); + stats_update(STATS_ARGS); + result = false; + goto out; + } + included_pch_file = pch_file; + } + free(relpath); i++; continue; @@ -2083,6 +2113,7 @@ cc_reset(void) free(secondary_config_path); secondary_config_path = NULL; free(current_working_dir); current_working_dir = NULL; free(profile_dir); profile_dir = NULL; + free(included_pch_file); included_pch_file = NULL; args_free(orig_args); orig_args = NULL; free(input_file); input_file = NULL; free(output_obj); output_obj = NULL; -- 1.7.7
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