To provide special features for the whole C family of languages.

§1. What makes a language C-like? This does:

void CLike::make_c_like(programming_language *pl) {
    METHOD_ADD(pl, PARSE_TYPES_PAR_MTID, CLike::parse_types);
    METHOD_ADD(pl, PARSE_FUNCTIONS_PAR_MTID, CLike::parse_functions);
    METHOD_ADD(pl, SUBCATEGORISE_LINE_PAR_MTID, CLike::subcategorise_code);

    METHOD_ADD(pl, ADDITIONAL_EARLY_MATTER_TAN_MTID, CLike::additional_early_matter);
    METHOD_ADD(pl, ADDITIONAL_PREDECLARATIONS_TAN_MTID, CLike::additional_predeclarations);

§2. Parsing. After a web has been read in and then parsed, code supporting its language is then called to do any further parsing it might want to. The code below is run if the language is "C-like": regular C and InC both qualify.

void CLike::parse_types(programming_language *self, web *W) {
    Find every typedef struct in the tangle2.1;
    Work out which structs contain which others2.2;

§2.1. We're going to assume that the C source code uses structures looking something like this:

    typedef struct fruit {
        struct pip the_pips[5];
        struct fruit *often_confused_with;
        struct tree_species *grows_on;
        int typical_weight;
    } fruit;

which adopts the traditional layout conventions of Kernighan and Ritchie. The structure definitions in this Inweb web all take the required form, of course, and provide many more examples.

Note that a fruit structure contains a pip structure (in fact, five of them), but only contains pointers to tree_species structures and itself. C requires therefore that the structure definition for pip must occur earlier in the code than that for fruit. This is a nuisance, so Inweb takes care of it automatically.

Find every typedef struct in the tangle2.1 =

    language_type *current_str = NULL;
    chapter *C;
    section *S;
    LOOP_WITHIN_TANGLE(C, S, Tangler::primary_target(W)) {
        if (Str::len(L->extract_to) == 0) {
            match_results mr = Regexp::create_mr();

            if (Regexp::match(&mr, L->text, U"typedef struct (%i+) %c*{%c*")) {
                current_str = Functions::new_struct(W, mr.exp[0], L);
                Tags::add_by_name(L->owning_paragraph, I"Structures");
            } else if ((Str::get_first_char(L->text) == '}') && (current_str)) {
                current_str->typedef_ends = L;
                current_str = NULL;
            } else if ((current_str) && (current_str->typedef_ends == NULL)) {
                Work through a line in the structure definition2.1.1;
            } else if ((Regexp::match(&mr, L->text, U"typedef %c+")) &&
                (Regexp::match(&mr, L->text, U"%c+##%c+") == FALSE)) {
                if (L->owning_paragraph->placed_very_early == FALSE)
                    L->category = TYPEDEF_LCAT;

§2.1.1. At this point we're reading a line within the structure's definition; for the sake of an illustrative example, let's suppose that line is:

    unsigned long long int *val;

We need to extract the element name, val, and make a note of it.

Work through a line in the structure definition2.1.1 =

    Str::copy(p, L->text);
    Remove C type modifiers from the front of p2.1.1.1;
    string_position pos = Str::start(p);
    if (Str::get(pos) != '/') {  a slash must introduce a comment here
        Move pos past the type name2.1.1.2;
        Move pos past any typographical type modifiers2.1.1.3;
        if (Str::in_range(pos)) {
            match_results mr = Regexp::create_mr();
            Copy the element name into elname2.1.1.4;
            Functions::new_element(current_str, elname, L);

§ The following reduces unsigned long long int *val; to just int *val;.

Remove C type modifiers from the front of p2.1.1.1 =

    inchar32_t *modifier_patterns[] = {
        U"(struct )(%C%c*)", U"(signed )(%C%c*)", U"(unsigned )(%C%c*)",
        U"(short )(%C%c*)", U"(long )(%C%c*)", U"(static )(%C%c*)", NULL };
    int seek_modifiers = TRUE;
    while (seek_modifiers) {
        seek_modifiers = FALSE;
        for (int i = 0; modifier_patterns[i]; i++)
            if (Regexp::match(&mr, p, modifier_patterns[i])) {
                Str::copy(p, mr.exp[1]);
                seek_modifiers = TRUE;

§ At this point p has been reduced to int *val;, but the following moves pos to point to the *:

Move pos past the type name2.1.1.2 =

    while ((Str::get(pos)) && (Characters::is_space_or_tab(Str::get(pos)) == FALSE))
        pos = Str::forward(pos);

§ And this moves it past the * to point to the v in int *val;:

Move pos past any typographical type modifiers2.1.1.3 =

    while ((Characters::is_space_or_tab(Str::get(pos))) || (Str::get(pos) == '*') ||
        (Str::get(pos) == '(') || (Str::get(pos) == ')')) pos = Str::forward(pos);

§ This then first copies the substring val; into elname, then cuts that down to just the identifier characters at the front, i.e., to val.

Copy the element name into elname2.1.1.4 =

    Str::substr(elname, pos, Str::end(p));
    if (Regexp::match(&mr, elname, U"(%i+)%c*")) Str::copy(elname, mr.exp[0]);

§2.2. Structure dependency. We say that S depends on T if struct S has an element whose type is struct T. That matters because if so then struct T has to be defined before struct S in the tangled output.

It's important to note that struct S merely having a member of type struct *T does not create a dependency. In the code below, because %i matches only identifier characters and * is not one of those, a line like

    struct fruit *often_confused_with;

will not trip the switch here.

Work out which structs contain which others2.2 =

    language_type *current_str;
    LOOP_OVER(current_str, language_type) {
        for (source_line *L = current_str->structure_header_at;
            ((L) && (L != current_str->typedef_ends));
            L = L->next_line) {
            match_results mr = Regexp::create_mr();
            if (Regexp::match(&mr, L->text, U" struct (%i+) %i%c*"))
                One structure appears to contain a copy of another one2.2.1;

§2.2.1. One structure appears to contain a copy of another one2.2.1 =

    text_stream *used_structure = mr.exp[0];
    language_type *str;
    LOOP_OVER_LINKED_LIST(str, language_type, W->language_types)
        if ((str != current_str) &&
            (Str::eq(used_structure, str->structure_name)))
            ADD_TO_LINKED_LIST(str, language_type, current_str->incorporates);

§3. Functions. This time, we will need to keep track of #ifdef and #endif pairs in the source. This matters because we will want to predeclare functions; but if functions are declared in conditional compilation, then their predeclarations have to be made under the same conditions.

The following stack holds the current set of conditional compilations which the source line being scanned lies within.

int cc_sp = 0;

void CLike::parse_functions(programming_language *self, web *W) {
    cc_sp = 0;
    chapter *C;
    section *S;
    LOOP_WITHIN_TANGLE(C, S, Tangler::primary_target(W))
        if ((L->category == CODE_BODY_LCAT) ||
            (L->category == BEGIN_DEFINITION_LCAT) ||
            (L->category == CONT_DEFINITION_LCAT)) {
            Look for conditional compilation on this line3.1;
            Look for a function definition on this line3.2;
    if (cc_sp > 0)
        Main::error_in_web(I"program ended with conditional compilation open", NULL);

§3.1. Look for conditional compilation on this line3.1 =

    match_results mr = Regexp::create_mr();
    if ((Regexp::match(&mr, L->text, U" *#ifn*def %c+")) ||
        (Regexp::match(&mr, L->text, U" *#IFN*DEF %c+"))) {
            Main::error_in_web(I"conditional compilation too deeply nested", L);
            cc_stack[cc_sp++] = L;
    if ((Regexp::match(&mr, L->text, U" *#endif *")) ||
        (Regexp::match(&mr, L->text, U" *#ENDIF *"))) {
        if (cc_sp <= 0)
            Main::error_in_web(I"found #endif without #ifdef or #ifndef", L);

§3.2. So, then, we recognise a C function as being a line which takes the form

    type identifier(args...

where we parse type only minimally. In InC (only), the identifier can contain namespace dividers written ::. Function declarations, we will assume, always begin on column 1 of their source files, and we expect them to take modern ANSI C style, not the long-deprecated late 1970s C style.

Look for a function definition on this line3.2 =

    if (!(Characters::is_space_or_tab(Str::get_first_char(L->text)))) {
        Str::copy(modified, L->text);
        Parse past any type modifiers3.2.1;
        match_results mr = Regexp::create_mr();
        if (Regexp::match(&mr, modified, U"(%i+) (%**)(%i+)%((%c*)")) {
            TEMPORARY_TEXT(ftype) Str::copy(ftype, mr.exp[0]);
            TEMPORARY_TEXT(asts) Str::copy(asts, mr.exp[1]);
            TEMPORARY_TEXT(fname) Str::copy(fname, mr.exp[2]);
            TEMPORARY_TEXT(arguments) Str::copy(arguments, mr.exp[3]);
            A function definition was found3.2.2;

§3.2.1. C has a whole soup of reserved words applying to types, but most of them can't apply to the return type of a function. We do, however, iterate so that forms like static long long int will work.

Parse past any type modifiers3.2.1 =

    inchar32_t *modifier_patterns[] = {
        U"(signed )(%C%c*)", U"(unsigned )(%C%c*)",
        U"(short )(%C%c*)", U"(long )(%C%c*)", U"(static )(%C%c*)", NULL };
    int seek_modifiers = TRUE;
    while (seek_modifiers) {
        seek_modifiers = FALSE;
        match_results mr = Regexp::create_mr();
        for (int i = 0; modifier_patterns[i]; i++)
            if (Regexp::match(&mr, modified, modifier_patterns[i])) {
                Str::concatenate(qualifiers, mr.exp[0]);
                Str::copy(modified, mr.exp[1]);
                seek_modifiers = TRUE; break;

§3.2.2. A function definition was found3.2.2 =

    Soak up further arguments from continuation lines after the declaration3.2.2.1;
    language_function *fn = Functions::new_function(fname, L);
    fn->function_arguments = Str::duplicate(arguments);
    WRITE_TO(fn->function_type, "%S%S %S", qualifiers, ftype, asts);
    if (Str::eq_wide_string(fn->function_name, U"isdigit")) fn->call_freely = TRUE;
    fn->no_conditionals = cc_sp;
    for (int i=0; i<cc_sp; i++) fn->within_conditionals[i] = cc_stack[i];

§ In some cases the function's declaration runs over several lines:

    void World::Subjects::make_adj_const_domain(inference_subject *infs,|
        instance *nc, property *prn) {|

Having read the first line, arguments would contain inference_subject *infs, and would thus be incomplete. We continue across subsequent lines until we reach an open brace {.

define MAX_ARG_LINES 32  maximum number of lines over which a function's header can extend

Soak up further arguments from continuation lines after the declaration3.2.2.1 =

    source_line *AL = L;
    int arg_lc = 1;
    while ((AL) && (arg_lc <= MAX_ARG_LINES) && (Regexp::find_open_brace(arguments) == -1)) {
        if (AL->next_line == NULL) {
            WRITE_TO(err_mess, "Function '%S' has a malformed declaration", fname);
            Main::error_in_web(err_mess, L);
        AL = AL->next_line;
        WRITE_TO(arguments, " %S", AL->text);
    int n = Regexp::find_open_brace(arguments);
    if (n >= 0) Str::truncate(arguments, n);

§4. Subcategorisation. The following is called after the parser gives every line in the web a category; we can, if we wish, change that for a more exotic one. We simply look for a #include of one of the ANSI C standard libraries.

void CLike::subcategorise_code(programming_language *self, source_line *L) {
    match_results mr = Regexp::create_mr();
    if (Regexp::match(&mr, L->text, U"#include <(%C+)>%c*")) {
        text_stream *library_file = mr.exp[0];
        inchar32_t *ansi_libs[] = {
            U"assert.h", U"ctype.h", U"errno.h", U"float.h", U"limits.h",
            U"locale.h", U"math.h", U"setjmp.h", U"signal.h", U"stdarg.h",
            U"stddef.h", U"stdio.h", U"stdlib.h", U"string.h", U"time.h",
        for (int j = 0; ansi_libs[j]; j++)
            if (Str::eq_wide_string(library_file, ansi_libs[j]))
                L->category = C_LIBRARY_INCLUDE_LCAT;

§5. Tangling extras. "Additional early matter" is used for the inclusions of the ANSI library files. We need to do that early, because otherwise types declared in them (such as FILE) won't exist in time for the structure definitions we will be tangling next.

It might seem reasonable to move all #include files up front this way, not just the ANSI ones. But that would defeat any conditional compilation around the inclusions; which Inform (for instance) needs in order to make platform-specific details to handle directories without POSIX in Windows.

void CLike::additional_early_matter(programming_language *self, text_stream *OUT, web *W, tangle_target *target) {
    chapter *C;
    section *S;
    LOOP_WITHIN_TANGLE(C, S, target)
        if (L->category == C_LIBRARY_INCLUDE_LCAT) {
            Tags::open_ifdefs(OUT, L->owning_paragraph);
            Tangler::tangle_line(OUT, L->text, S, L);
            Tags::close_ifdefs(OUT, L->owning_paragraph);

§6. Tangling predeclarations. This is where a language gets the chance to tangle predeclarations, early on in the file. We use it first for the structures, and then the functions — in that order since the function types likely involve the typedef names for the structures.

void CLike::additional_predeclarations(programming_language *self, text_stream *OUT, web *W) {
    Predeclare the structures in a well-founded order6.2;
    Predeclare simple typedefs6.1;
    Predeclare the functions6.4;

§6.1. A "simple typedef" here means one that is aliasing something other than a structure: for example typedef unsigned int uint; would be a simple typedef.

Predeclare simple typedefs6.1 =

    chapter *C;
    section *S;
    LOOP_WITHIN_TANGLE(C, S, Tangler::primary_target(W))
        if (L->category == TYPEDEF_LCAT) {
            Tags::open_ifdefs(OUT, L->owning_paragraph);
            LanguageMethods::tangle_line(OUT, W->main_language, L->text);
            Tags::close_ifdefs(OUT, L->owning_paragraph);

§6.2. It's easy enough to make sure structures are tangled so that inner ones precede outer, but we need to be careful to be terminating if the source code we're given is not well founded because of an error by its programmer: for example, that structure A contains B contains C contains A. We do this with the tangled flag, which is FALSE if a structure hasn't been started yet, NOT_APPLICABLE if it's in progress, and TRUE if it's finished.

Predeclare the structures in a well-founded order6.2 =

    language_type *str;
    LOOP_OVER_LINKED_LIST(str, language_type, W->language_types)
        str->tangled = FALSE;
    LOOP_OVER_LINKED_LIST(str, language_type, W->language_types)
        CLike::tangle_structure(OUT, self, str);

§6.3. Using the following recursion, which is therefore terminating:

void CLike::tangle_structure(OUTPUT_STREAM, programming_language *self, language_type *str) {
    if (str->tangled != FALSE) return;
    str->tangled = NOT_APPLICABLE;
    language_type *embodied = NULL;
    LOOP_OVER_LINKED_LIST(embodied, language_type, str->incorporates)
        CLike::tangle_structure(OUT, self, embodied);
    str->tangled = TRUE;
    Tags::open_ifdefs(OUT, str->structure_header_at->owning_paragraph);
    LanguageMethods::insert_line_marker(OUT, self, str->structure_header_at);
    for (source_line *L = str->structure_header_at; L; L = L->next_line) {
        WRITE("%S\n", L->text);
        L->suppress_tangling = TRUE;
        if (L == str->typedef_ends) break;
    Tags::close_ifdefs(OUT, str->structure_header_at->owning_paragraph);

§6.4. Functions are rather easier to deal with. In general, if a function was defined within some number of nested #ifdef or #ifndef directives, then we reproduce those around the predeclaration: except, as a special trick, if the line contains a particular comment. For example:

    #ifdef SOLARIS /* inweb: always predeclare */

That exempts any functions inside this condition from meeting the condition in order to be predeclared. It's a trick used in the foundation module just a couple of times: the idea is that although a definition of the functions is given which only works under SOLARIS, an external piece of code will provide alternative function definitions which would work without SOLARIS. The functions therefore need predeclaration regardless, because they will exist either way.

Predeclare the functions6.4 =

    chapter *C;
    section *S;
    LOOP_WITHIN_TANGLE(C, S, Tangler::primary_target(W))
        if (L->function_defined) {
            if (L->owning_paragraph == NULL) {
                WRITE_TO(err_mess, "Function '%S' seems outside of any paragraph",
                Main::error_in_web(err_mess, L);
            if (L->owning_paragraph->placed_very_early == FALSE) {
                language_function *fn = L->function_defined;
                int to_close = 0;
                for (int i=0; i<fn->no_conditionals; i++) {
                    match_results mr = Regexp::create_mr();
                    if (!(Regexp::match(&mr, fn->within_conditionals[i]->text,
                        U"%c*inweb: always predeclare%c*"))) {
                        WRITE("%S\n", fn->within_conditionals[i]->text);
                Tags::open_ifdefs(OUT, L->owning_paragraph);
                LanguageMethods::insert_line_marker(OUT, W->main_language, L);
                WRITE("%S ", fn->function_type);
                LanguageMethods::tangle_line(OUT, W->main_language, fn->function_name);
                WRITE("(%S;\n", fn->function_arguments);
                Tags::close_ifdefs(OUT, L->owning_paragraph);
                for (int i=0; i<to_close; i++) {

§7. Overriding regular code weaving. We have the opportunity here to sidestep the regular weaving algorithm, and do our own thing. We decline.