Expose clang resource/include directory through CMake variable

[tristan957]

I am using libclang to parse C source files. Given a small program like:

#include <stddef.h>

int main(void)
{
  size_t hello = 5;
  return hello;
}

libclang should report fatal error: 'stddef.h' file not found.

On my system (Fedora 36), the resource directory is located:

$ clang -print-resource-dir
/usr/lib64/clang/14.0.5

Which means the include directory is located at $(clang -print-resource-dir)/include). The clang cmake modules already expose a variable called CLANG_INCLUDE_DIRS, but the only directory exposed in this variable is $CMAKE_INSTALL_PREFIX/include, which isn't helpful for what I need.

Ideally these constants would be exposed in a cross buildsystem way like #9777, but I am willing to settle for just appending to the CLANG_INCLUDE_DIRS array since that should be as little effort as possible to solve what I need.

[efriedma-quic]

Normal usage patterns of libclang should normally find clang's resource directory without requiring you to explicitly pass it in. If that isn't happening, something has gone wrong. See CIndexer::getClangResourcesPath.

[tristan957]

Here is how I am using libclang

    database = clang_CompilationDatabase_fromDirectory(builddir, &error);
    if (error) {
        fprintf(stderr, "Failed to read the compilation database\n");
        return EX_IOERR;
    }

int
mock_collect(const char *file)
{
    char **argv;
    CXIndex index;
    CXCursor cursor;
    unsigned int argc;
    enum CXErrorCode ret;
    CXTranslationUnit tu;
    unsigned int real_argc;
    CXCompileCommand command;
    CXCompileCommands commands;

    commands = clang_CompilationDatabase_getCompileCommands(database, file);
    if (clang_CompileCommands_getSize(commands) != 1) {
        fprintf(stderr, "More than one series of compile commands detected for %s\n", file);
        return EX_SOFTWARE;
    }
    command = clang_CompileCommands_getCommand(commands, 0);

    argc = clang_CompileCommand_getNumArgs(command);
    argv = calloc(argc + 2, sizeof(*argv));
    argv[0] = "-DHSE_MOCK=__attribute__((__annotate__(\"mock\")))";
    argv[1] = "-I";
    argv[2] = includedir; // $resourcedir/include
    real_argc = 3;
    for (unsigned int i = 1; i < argc; i++) {
        CXString arg = clang_CompileCommand_getArg(command, i);
        const char *arg_data = clang_getCString(arg);

        /* Ignore warnings */
        if (strstr(arg_data, "-W") == arg_data)
            continue;

        argv[real_argc++] = strdup(arg_data);

        clang_disposeString(arg);
    }

    index = clang_createIndex(0, 1);
    ret = clang_parseTranslationUnit2(index, file, (const char **)argv, real_argc - 1, NULL, 0, 0,
        &tu);
    if (ret) {
        fprintf(stderr, "Failed to parse the translation unit: %d\n", ret);
        return EX_SOFTWARE;
    }

    cursor = clang_getTranslationUnitCursor(tu);
    clang_visitChildren(cursor, visit_tu, NULL);

    clang_disposeTranslationUnit(tu);
    clang_disposeIndex(index);
    clang_CompileCommands_dispose(commands);

    for (unsigned int i = 3; i < real_argc; i++)
        free(argv[i]);
    free(argv);

    return 0;
}

I just started using libclang, so I don't know what I might be doing wrong. I can point at the repository this exists in, but this is pretty much everything.

[tristan957]

I tried switching to clang_parseTranslationUnit2FullArgv(), but that just has the same problems.

[tristan957]

Here is a command like which I pass to clang_parse...().

clang -Ilib/libhse-3.so.3.1.0.p -Ilib -I../lib -Ilib/include -I../lib/include -Iinclude -I../include -Ilib/util/include -I../lib/util/include -Ilib/mpool/include -I../lib/mpool/include -Isubprojects/xxHash-0.8.1 -I../subprojects/xxHash-0.8.1 -Isubprojects/lz4-1.9.3/lib -I../subprojects/lz4-1.9.3/lib -Isubprojects/cJSON-1.7.15/include-workaround-meson -I../subprojects/cJSON-1.7.15/include-workaround-meson -Isubprojects/hyperloglog -I../subprojects/hyperloglog -Ilib/error/include -I../lib/error/include -Ilib/logging/include -I../lib/logging/include -Ilib/pidfile/include -I../lib/pidfile/include -Ilib/rest/include -I../lib/rest/include -Isubprojects/rbtree -I../subprojects/rbtree -Isubprojects/crc32c -I../subprojects/crc32c -Isubprojects/xoroshiro -I../subprojects/xoroshiro -fvisibility=hidden -fcolor-diagnostics -D_FILE_OFFSET_BITS=64 -O0 -g -fmacro-prefix-map=../= -DDEBUG_RCU -fstack-protector-all -DHSE_BUILD_DEBUG -D_GNU_SOURCE -D_LGPL_SOURCE -DLOG_DEFAULT=7 -DLEVEL1_DCACHE_LINESIZE=64 -DURCU_INLINE_SMALL_FUNCTIONS -fPIC -pthread -DXXH_INLINE_ALL -DXXH_STATIC_LINKING_ONLY -MD -MQ lib/libhse-3.so.3.1.0.p/util_lib_dax.c.o -MF lib/libhse-3.so.3.1.0.p/util_lib_dax.c.o.d -c -x c-header -std=gnu11 /home/tpartin/Projects/hse/lib/util/include/hse/util/dax.h -DHSE_MOCK=__attribute__((__annotate__("mock"))) -I /usr/lib64/clang/14.0.5/include

Note that the last 2 arguments are me trying to work around this issue

[efriedma-quic]

Looks like the relevant bits were last touched in https://reviews.llvm.org/D124815 . CC @aykevl

[tristan957]

I appreciate your help up to this point with my issue :)

[aykevl]

@efriedma-quic true, but the patch should only have an effect when dladdr returns NULL - and thus only turn a crash into a non-crash. So I doubt it's related to this bug.