path: root/src-cslul/main.c

/*

  main.c -- Entry point for CSLUL compiler

  Copyright © 2020-2024 Samuel Lidén Borell <samuel@kodafritt.se>

  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:

  The above copyright notice and this permission notice shall be included in
  all copies or substantial portions of the Software.

  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
  LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
  THE SOFTWARE.

*/

#include "cslul.h"
#include "defaults.h"
#include <stdlib.h>
#include <string.h>
#include <errno.h>
#include <assert.h>
#include <stdio.h>
#include <limits.h>

#ifdef CSLUL_WINDOWS
#define NO_GETTEXT
#endif

#ifndef NO_GETTEXT
#    include <locale.h>
#    include <libintl.h>
#    define _(x) gettext(x)
#else
#    define gettext(x) (x)
#    define _(x) (x)
#endif
/* () in array initializers give a warning */
#define TR(x) x

static const char *progname;
static struct CSlulConfig *cfg;
static int reported_error = 0;
static int error_limit = 1;
static int errors_left = 50;
static int accept_errors = 0;
static int errout_set;
static FILE *errout;

static const char levels[][13] = {
    TR("fatal error"), TR("error"), TR("warning"), TR("hint"), TR("style remark")
};

static const char supported_attrs[] =
"        \\slul \\name \\type \\version \\repo \\repo.mirror \\website\n"
"        \\license \\license.text \\license.list \\depends\n"
"        \\interface_depends \\api_def \\source\n";

static const char supported_apidef_flags[] =
"        retracted\n";

static struct {
    unsigned bad_attr_name : 1;
    unsigned attr_order : 1;
    unsigned too_many_attr_params : 1;
    unsigned depflag_order : 1;
    /* TODO bad dep/ifacedep flag */
    unsigned specwithsource : 1;
    unsigned bad_arch_format : 1;
    unsigned string_too_long : 1;
    unsigned escape_too_long : 1;
    unsigned bad_number_type : 1;
    unsigned bad_expr_token : 1;
    unsigned repeated_case : 1;
    unsigned unsupported_langver : 1;
    unsigned langver_syntax : 1;
    unsigned attr_char : 1;
    unsigned optional_non_ref : 1;
    unsigned bad_param_type : 1;
    unsigned bad_tldata_qual : 1;
    unsigned ambiguous_ident : 1;
    unsigned ambiguouos_expr_type : 1;
    unsigned bad_apidef_flag : 1;
    unsigned no_goto_predecessor : 1;
    unsigned invalid_start_token : 1;
    unsigned versioned_closed_type : 1;
    unsigned no_since : 1;
    unsigned repeated_since : 1;
    unsigned method_constr : 1;
    unsigned ml_comment_not_closed : 1;
    unsigned ident_later_but_lower : 1;
    unsigned slulapp_main_missing : 1;
    unsigned cant_access_optional : 1;
} shown_hint;

/** Counts the number of parameters in a format string */
static int num_fmt_params(const char *fmt)
{
    const char *s = fmt;
    int count = 0;
    while (*s) {
        s += strcspn(s, "%");
        if (!*s) break;
        s++;
        if (*s != '%') count++;
        else s++;
    }
    return count;
}

static int endswith_path(const char *filename, const char *end)
{
    size_t endlen = strlen(end);
    size_t pathlen = strlen(filename);
    return pathlen >= endlen &&
        !strcmp(end, &filename[pathlen-endlen]) &&
        (pathlen == endlen ||
            filename[pathlen-endlen-1] == '/' ||
            filename[pathlen-endlen-1] == '\\');
}

static void report_system_err(int saved_errno, const char *msgtext)
{
    errno = saved_errno;
    perror(msgtext);
}

static void msghandler(const struct CSlulState *st)
{
    /* XXX if we add multi-threaded compilation, then this function requires
           a lock for stderr so messages don't get intertwined */
    /* FIXME stderr is unbuffered, so this can still cause intertwined
             messages if multiple processes write to the terminal/file
             that stderr uses. */
    const char *filename = st->locs[0].filename;
    const char *level;
    enum CSlulErrorCode errcode = st->errorcode;
    const char *msgtext;
    int saved_errno = errno;

    if (errcode == CSLUL_E_OPENFILE && !strcmp(filename, "main.slul")) {
        fprintf(errout, "%s\n%s",
            _("No 'main.slul' file was found in the current directory"),
#if 0
            _("See 'man main.slul' for documentation.\n")
#else
            ""
#endif
            );
        goto error_printed;
    }

    level = gettext(levels[st->level]);
    msgtext = gettext(cslul_lookup_message(errcode));
    /* Print "filename:line.column: errorlevel: " */
    if (filename) {
        fprintf(errout, "%s:%.0d%s%.0d%s %s: ", filename,
                st->locs[0].line, st->locs[0].line?".":"", st->locs[0].column,
                st->locs[0].line?":":"", level);
    } else {
        fprintf(errout, "%s: ", level);
    }
    /* Print main error message */
    if (errcode == CSLUL_E_OPENFILE) {
        /* no need to also say that the open operation failed */
        report_system_err(saved_errno, NULL);
    } else if (errcode == CSLUL_E_OUTOFMEMORY) {
        /* no point in calling perror here */
        fprintf(errout, "%s\n", msgtext);
    } else if (CSLUL_IS_SYSTEM_ERR(errcode)) {
        report_system_err(saved_errno, msgtext);
    } else if (CSLUL_IS_INTERNAL_ERR(errcode)) {
        /* Message is a format string */
        fprintf(errout, _("Internal compiler error: %s_%02x\n"),
                msgtext, CSLUL_GET_INTERR_MINOR_CODE(errcode));
        #ifdef FUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION
        abort();
        #endif
    } else {
        int num_fmt = num_fmt_params(msgtext);
        int i;
        assert(num_fmt <= CSLUL_MAX_LOCATIONS);
        switch (num_fmt) {
        case 0:
            fputs(msgtext, errout);
            break;
        case 1:
            fprintf(errout, msgtext, st->locs[0].length, st->locs[0].text);
            break;
        case 2:
            fprintf(errout, msgtext, st->locs[0].length, st->locs[0].text,
                    st->locs[1].length, st->locs[1].text);
            break;
        case 3:
            fprintf(errout, msgtext, st->locs[0].length, st->locs[0].text,
                    st->locs[1].length, st->locs[1].text,
                    st->locs[2].length, st->locs[2].text);
            break;
        case 4:
            fprintf(errout, msgtext, st->locs[0].length, st->locs[0].text,
                    st->locs[1].length, st->locs[1].text,
                    st->locs[2].length, st->locs[2].text,
                    st->locs[3].length, st->locs[3].text);
            break;
        case 5:
            fprintf(errout, msgtext, st->locs[0].length, st->locs[0].text,
                    st->locs[1].length, st->locs[1].text,
                    st->locs[2].length, st->locs[2].text,
                    st->locs[3].length, st->locs[3].text,
                    st->locs[4].length, st->locs[4].text);
            break;
        default:
            assert(0);
        }
        fputc('\n', errout);
        i = num_fmt > 1 ? num_fmt : 1;
        for (; i < CSLUL_MAX_LOCATIONS; i++) {
            const struct CSlulLocation *loc = &st->locs[i];
            static const char loctype_texts[][18] = {
                /* CSLUL_LT_INVALID */     "",
                /* CSLUL_LT_MAIN */        TR("main location"),
                /* CSLUL_LT_MAINTEXT */    TR("main location"),
                /* CSLUL_LT_DEFINITION */  TR("definition"),
                /* CSLUL_LT_DEFINED IN */  TR("defined in"),
                /* CSLUL_LT_DEPENDENCY */  TR("depends on"),
                /* CSLUL_LT_MINIMUM */     TR("minimum"),
                /* CSLUL_LT_INSTALLED */   TR("installed version"),
                /* CSLUL_LT_DUPLICATE */   TR("other definition"),
                /* CSLUL_LT_EXPR_LEFT */   TR("left expression"),
                /* CSLUL_LT_EXPR_RIGHT */  TR("right expression"),
                /* CSLUL_LT_TYPE_SOURCE */ TR("source type"),
                /* CSLUL_LT_TYPE_TARGET */ TR("target type")
            };
            const char *typetext;
            if (loc->type == CSLUL_LT_INVALID) break;
            typetext = gettext(loctype_texts[loc->type]);
            fprintf(errout, "%s:%.0d%s%.0d%s <-- %s%s %.*s\n", loc->filename,
                loc->line, loc->line?".":"", loc->column,
                loc->line?":":"", typetext,
                loc->text?":":"",
                loc->text?loc->length:0, loc->text?loc->text:"");
        }
    }

    switch ((int)errcode) {
    case CSLUL_E_BADATTRNAME:
        if (!shown_hint.bad_attr_name) {
            shown_hint.bad_attr_name = 1;
            fprintf(errout, _("        The following attributes are supported:\n"));
            fprintf(errout, supported_attrs);
        }
        break;
    case CSLUL_E_WRONGATTRORDER:
        if (!shown_hint.attr_order) {
            shown_hint.attr_order = 1;
            fprintf(errout, _("        Attributes should come in this order:\n"));
            fprintf(errout, supported_attrs);
        }
        break;
    case CSLUL_E_TOOMANYATTRPARAMS:
        if (!shown_hint.too_many_attr_params) {
            shown_hint.too_many_attr_params = 1;
            fprintf(errout, _(
"        Note that the values may not contain spaces\n"));
        }
        break;
    case CSLUL_E_DEPFLAGSORDER:
    case CSLUL_E_IFACEDEPFLAGSORDER:
        if (!shown_hint.depflag_order) {
            shown_hint.depflag_order = 1;
            fprintf(errout, _("        The flags should come in this order:\n"));
            /* TODO remove/revise the bundled and optional flags? */
            fprintf(errout,
"        bundled -> unstable -> optional -> nestedonly\n");
        }
        break;
    case CSLUL_E_MAXSOURCEFILES:
        fprintf(errout, _(
"        Please try to divide the module into smaller modules.\n"
"        This limitation is here to prevent editors and other tools from\n"
"        encountering problems when working with the 'main.slul' file.\n"));
        break;
    case CSLUL_E_SPECWITHSOURCE:
        if (!shown_hint.specwithsource) {
            shown_hint.specwithsource = 1;
            fprintf(errout, _(
"        Modules of these types should not contain any implementation.\n"));
        }
        break;
    case CSLUL_E_BADARCHFORMAT:
        if (!shown_hint.bad_arch_format) {
            shown_hint.bad_arch_format = 1;
            fprintf(errout, _(
"        Please use a multiarch triple: cpu-syscalltype-abitype\n"
"        For example: x86_64-linux-gnu\n"
"        To build for several target systems, separate them with commas.\n"));
        }
        break;
    case CSLUL_E_STRINGTOOLONG:
        if (!shown_hint.string_too_long) {
            shown_hint.string_too_long = 1;
            fprintf(errout, _(
"        Please break into multiple pieces:\n"
"        \"like\"\n"
"        \"this\"\n"));
        }
        break;
    case CSLUL_E_ESCAPETOOLONG:
        if (!shown_hint.escape_too_long) {
            shown_hint.escape_too_long = 1;
            fprintf(errout, _(
"        If you want any of the characters 0-9, A-F, a-f to follow a hex\n"
"        escape sequence, please split the string. For example:\n"
"        \"...\\xFF\" \"F...\"\n"));
        }
        break;
    case CSLUL_E_BADNUMBERTYPE:
        if (!shown_hint.bad_number_type) {
            shown_hint.bad_number_type = 1;
            fprintf(errout, _(
"        The syntax for numbers is: (_ is an optional separator)\n"
"        123_456_789 - for decimal (base 10)\n" /* TODO floating point */
"        0x1234_ABCD - for hexadecimal (base 16)\n"
"        0b1010_1111 - for binary (base 2)\n"));
        }
        break;
    case CSLUL_E_BADEXPRTOKEN:
        if (!shown_hint.bad_expr_token) {
            shown_hint.bad_expr_token = 1;
            fprintf(errout, _(
"        This can happen if a line break is missing\n"));
        }
        break;
    case CSLUL_E_REPEATEDCASE:
        if (!shown_hint.repeated_case) {
            shown_hint.repeated_case = 1;
            fprintf(errout, _(
"        To match multiple values, use comma:\n"
"            case 123, 456:\n"
"        To have an empty case, use an empty block:\n"
"            case 123: {}\n"));
        }
        break;
    case CSLUL_E_UNSUPPORTEDLANGVER:
    case CSLUL_E_UNSUPPORTEDIMPLLANGVER:
        if (!shown_hint.unsupported_langver) {
            shown_hint.unsupported_langver = 1;
            fprintf(errout, _(
"        The supported language versions are:\n"));
            fprintf(errout, _(
"        %s\n"), cslul_supported_langver());
        }
        break;
    case CSLUL_E_BADLANGVERSYNTAX:
        if (!shown_hint.langver_syntax) {
            shown_hint.langver_syntax = 1;
            fprintf(errout, _(
"        The syntax is \"\\slul MINIMUM-VERSION impl IMPL-VER upto MAX-VER\".\n"
"        Only the \"\\slul MINIMUM-VERSION\" part is mandatory.\n"));
        }
        break;
    case CSLUL_E_BADATTRCHAR:
        if (!shown_hint.attr_char) {
            shown_hint.attr_char = 1;
            fprintf(errout, _(
"        Use spaces to separate attribute names and values.\n"));
        }
        break;
    case CSLUL_E_OPTIONALNONREF:
        if (!shown_hint.optional_non_ref) {
            shown_hint.optional_non_ref = 1;
            fprintf(errout, _(
"        These are written as ?ref, ?arena and ?own\n"));
        }
        break;
    case CSLUL_E_BADPARAMTYPE:
        if (!shown_hint.bad_param_type) {
            shown_hint.bad_param_type = 1;
            fprintf(errout, _(
"        Type parameters must specify one of the following types:\n"
"        ref T, arena T, own T or enum T\n"));
        }
        break;
    case CSLUL_E_BADTLDATAQUAL:
        if (!shown_hint.bad_tldata_qual) {
            shown_hint.bad_tldata_qual = 1;
            fprintf(errout, _(
"        Top level data objects are always const and non-shared.\n"));
        }
        break;
    case CSLUL_E_AMBIGUOUSIDENT:
        if (!shown_hint.ambiguous_ident) {
            shown_hint.ambiguous_ident = 1;
            /* TODO actually implement the \rename attribute */
/*            fprintf(errout, _(
"        Add \\rename in the module header to rename one of the identifiers.\n"
"        The syntax is \\rename MODULENAME FROM TO\n"));*/
        }
        break;
    case CSLUL_E_AMBIGUOUSEXPRTYPE:
        if (!shown_hint.ambiguouos_expr_type) {
            shown_hint.ambiguouos_expr_type = 1;
            fprintf(errout, _(
            /* TODO for == and !=, the/an expr with known type should come on the left side */
            /* FIXME how to make e.g. x<y+1 convenient to use? */
"        You can put the value in a variable to explicitly set the type.\n"));
        }
        break;
    case CSLUL_E_BADAPIDEFFLAG:
        if (!shown_hint.bad_apidef_flag) {
            shown_hint.bad_apidef_flag = 1;
            fprintf(errout, _(
"        Supported flags are:\n"));
            fprintf(errout, supported_apidef_flags);
        }
        break;
    case CSLUL_E_NOGOTOPREDECESSOR:
        if (!shown_hint.no_goto_predecessor) {
            shown_hint.no_goto_predecessor = 1;
            fprintf(errout, _(
"        A goto target must have either of the following:\n"
"          1. a preceeding statement that continues to the target,\n"
"          2. a goto to it anywhere before it,\n"
"          3. or, it can be the first statement in a function.\n"
"        This is necessary to infer the states of the variables.\n"));
        }
        break;
    case CSLUL_E_BADTOPLEVELTOKEN:
        if (!shown_hint.invalid_start_token) {
            shown_hint.invalid_start_token = 1;
            /* FIXME "since" is valid too, but only in (versioned) interfaces */
            fprintf(errout, _(
"        Valid start tokens are: type, data, func.\n"));
        }
        break;
    case CSLUL_E_VERSIONEDCLOSEDTYPE:
        if (!shown_hint.versioned_closed_type) {
            shown_hint.versioned_closed_type = 1;
            fprintf(errout, _(
"        Closed types cannot change if they are exported, so it does not\n"
"        make sense to put since-versions inside them.\n"));
        }
        break;
    case CSLUL_E_NOSINCE:
    case CSLUL_E_MISSINGVERWITHAPIDEF:
        if (!shown_hint.no_since) {
            shown_hint.no_since = 1;
            fprintf(errout, _(
"        If you are working on an unstable version, please set \"\\version ... unstable\".\n"));
        }
        break;
    case CSLUL_E_REPEATEDSINCE:
        if (!shown_hint.repeated_since) {
            shown_hint.repeated_since = 1;
            fprintf(errout, _(
"        To specify multiple versions (e.g. for backports),\n"
"        use syntax like this: \"since { 1.0 1.2 }\"\n"));
        }
        break;
    case CSLUL_E_METHODCONSTR:
        if (!shown_hint.method_constr) {
            shown_hint.method_constr = 1;
            fprintf(errout, _(
"        Call constructors like this \"Type obj = .new()\".\n"));
        }
        break;
    case CSLUL_E_MLCOMMENTNOTCLOSED:
        if (!shown_hint.ml_comment_not_closed) {
            shown_hint.ml_comment_not_closed = 1;
            fprintf(errout, _(
"        The closing #}} must be placed at the start of a line.\n"));
        }
        break;
    case CSLUL_E_TLTYPELATERLOWER:
    case CSLUL_E_TLIDENTLATERLOWER:
        if (!shown_hint.ident_later_but_lower) {
            shown_hint.ident_later_but_lower = 1;
            fprintf(errout, _(
"        There's no higher \\abi_def after the lower (but more recent)\n"
"        \\api_def in the dependency.\n"));
        }
        break;
    case CSLUL_E_APPWITHOUTMAIN:
    case CSLUL_E_MAINMALFORMED:
        if (!shown_hint.slulapp_main_missing) {
            shown_hint.slulapp_main_missing = 1;
            /* TODO the SlulApp object should have the "arena" qualifier,
                    but that isn't implemented yet. */
            fprintf(errout, _(
"        The definition should look like this:\n"
"        func SlulApp.main() -> SlulExitStatus\n"));
        }
        break;
    case CSLUL_E_CANTACCESSOPTIONAL:
        if (!shown_hint.cant_access_optional) {
            shown_hint.cant_access_optional = 1;
            fprintf(errout, _(
"        Put the subexpression value in a ?ref variable, check that it\n"
"        isn't 'none', and then access the value via the variable.\n"));
        }
        break;
    default:;
    }
  error_printed:
    if (st->level <= CSLUL_L_ERROR && error_limit && !errors_left--) {
        exit(EXIT_FAILURE);
    }
    if (CSLUL_IS_INTERNAL_ERR(errcode) || errcode == CSLUL_E_OUTOFMEMORY) {
        exit(EXIT_FAILURE);
    }
}

static void show_help(void)
{
    printf(_("usage: %s [OPTION]... [MODULE-ROOT]\n"
"\n"
"C-SLUL: A compiler for SLUL implemented in C.\n"
"\n"
"Without arguments, the module in the current directory is compiled.\n"
"Or, optionally, a path for one or more modules may be specified.\n"
"\n"
"Options:\n\n"), progname);
    puts(_(
"  --outdir DIR  Write output files to this directory instead of the source\n"
"                directory."));
    puts(_(
"  -t TYPE       Override the type of output to generate from the module\n"
"                ('-t help' for list)"));
    puts(_(
"  --target NAME Cross-compile to other target platforms. The platform names\n"
"                should be multiarch triples, e.g. x86_64-linux-gnu,\n"
"                separated by comma."));
    printf(_(
"  -I DIRECTORY  Use an alternative directory with interface files.\n"
"                Specify '-I -' to skip the default ones, which are:\n"
"                %s%s%s%s\n"),
#ifdef NO_DEFAULT_IFACEDIRS
SLULIFACEDIR, "","",""
#elif defined(CSLUL_WINDOWS)
/* TODO "%APPDATA%\\slul-interfaces, %CommonProgramFiles%\\slul-interfaces, "*/
"%APPROOT%\\slul-interfaces", "","",""
#else
"~/.local/share/slul-interfaces",
(sizeof(SLULIFACEDIR) > 1 ?
    ", " SLULIFACEDIR : ""),
(sizeof(USRLOCAL_SLULIFACEDIR) > 1 &&
    strcmp(USRLOCAL_SLULIFACEDIR, SLULIFACEDIR) ?
    ", " USRLOCAL_SLULIFACEDIR : ""),
(sizeof(USR_SLULIFACEDIR) > 1 &&
    strcmp(USR_SLULIFACEDIR, SLULIFACEDIR) ?
    ", " USR_SLULIFACEDIR : "")
#endif
        );
    puts(_(
"  --error-limit=N Stop after N errors (0=no limit. Default: 50)."));
    puts(_(
"  --error-output=FILE Redirect compiler errors to a file (\"-\" for stdout)"));
    puts(_(
"  -q            Hide all warnings. For more fine-grained control,\n"
"                use: --message-level=fatal/error/warning/notice/style\n"
"                and --no-hints"));
    puts(_(
"  -V, --version Shows the compiler version, and the supported SLUL language\n"
"                versions."));
    printf("\n");
/* TODO
"\n"
"For help type 'man cslul' or visit https://slul.kodafritt.se/\n"
*/
}

static void show_outtype_help(void)
{
    puts(_(
"List of choices for -t:\n"
"  auto     - Automatically select based on module type (default).\n"
"  check    - Just perform checks (doesn't generate any output files).\n"
"  objfile  - Generate an object file (a single one for the whole module).\n"
"  library  - Generate dynamic and static libraries.\n"
"  dynlib   - Generate a dynamic library only.\n"
"  statlib  - Generate a static library only.\n"
"  header   - Generate a C header file.\n"
"  plugin   - Generate a plugin (for some other application)."));
    puts(_(
"  exe      - Generate an application executable.\n"
"\n"
"Not all kinds of outputs are possible for all modules types.\n"
));
}

static void show_version(void)
{
    const char *langvers = cslul_supported_langver();
    printf(_("cslul compiler version: %s\n"
             "\n"
             "Supported SLUL language versions:\n"
             "%s\n"),
             CSLUL_VERSION_STR,
             langvers);
}

static void invalid_option(const char *arg)
{
    fprintf(stderr, _("%s: invalid option: %s\n"), progname, arg);
}

static int process_module(char *path)
{
    struct CSlul *cslul;
    int ok;
    if (path && endswith_path(path, "main.slul")) {
        size_t len = strlen(path);
        if (len >= 10) { /* ends with /main.slul */
            path[len-9] = '\0';
        } else { /* is exactly main.slul */
            path = NULL; /* = current directory */
        }
    }
    cslul = cslul_create(cfg);
    if (!cslul) return 0;

    ok = cslul_build(cslul, path);
    cslul_free(cslul);
    return ok;
}

static int process_modules(int argc, char **argv)
{
    int optparse = 1;
    int has_args = 0;
    int argleft;
    int ok = 1;
    char **argp;

    /* Loop through all filename arguments */
    optparse = 1;
    for (argleft = argc-1, argp = argv+1; argleft>0; argleft--, argp++) {
        char *arg = *argp;
        if (arg[0] == '-') {
            if (arg[1] == '\0') {
                /* TODO best way to implement this?
                    - mocking open function could be tricky (it is already passed into cfg.prms at this point).
                    - perhaps a function could be added in cslul.h:
                        cslul_set_single_file(struct CSlul *ctx, CSlulFile file, const char *filename);
                    - such files cannot be libraries, and cannot have \source references
                    - the file should be closed also.
                    - should this also run the program? or only compile it? or interpret it?
                    - use something similar to readline?
                      or better, simply let users who want readline use a
                      wrapper such as rlfe, rlwrap, ledit
                    - allow even \slul to be skipped?
                    - how about Windows? winlibc.c does not have a stdin variable/file
                      (but that would be easy to add)
                    - can line-based input be done easily? that should
                      only be done for the main "file", not for interfaces.
                ---> Alternative solution: Add a low level "pipe mode",
                     plus a separate program, that can use readline and/or
                     allow editing (maybe even a full IDE, with a "quick
                     one file compilation" mode?)
                     - The client needs to initiate the requests.
                     - A "memory snapshot" function could be useful for IDEs
                     - Input should be raw UTF-8, even on Windows. */
                fprintf(stderr, _("%s: parsing from standard in is currently not supported\n"), progname);
                return 0;
            } else if (optparse) {
                if (arg[1] == '-') {
                    if (arg[2] == '\0') optparse = 0;
                } else if (arg[1] == '=') { /* modified by option parser */
                    argleft--;
                    argp++;
                }
                continue;
            }
        }
        if (!*arg) {
            fprintf(stderr, _("%s: empty string given as module root directory\n"), progname);
        } else if (!process_module(arg)) {
            if (!strcmp(arg, "/?")) {
                fprintf(stderr, _("Type \"%s --help\" for help.\n"), progname);
            }
            if (error_limit && !errors_left) return 0;
            ok = 0;
        }
        has_args = 1;
    }

    if (!has_args) {
        return process_module(NULL);
    }
    return ok;
}

static int check_duplicate_arg(const char *argname, int *statusflag)
{
    if (*statusflag) {
        fprintf(stderr, _("%s: Parameter --%s may only be specified once\n"),
                progname, argname);
        reported_error = 1;
        return 0;
    } else {
        *statusflag = 1;
        return 1;
    }
}

static int set_msglevel(const char *value)
{
    enum CSlulMessageLevel msglevel;
    if (!strcmp(value, "fatal")) msglevel = CSLUL_L_FATAL;
    else if (!strcmp(value, "error")) msglevel = CSLUL_L_ERROR;
    else if (!strcmp(value, "warning")) msglevel = CSLUL_L_WARNING;
    else if (!strcmp(value, "notice")) msglevel = CSLUL_L_NOTICE;
    else if (!strcmp(value, "style")) msglevel = CSLUL_L_STYLE;
    else {
        return 0;
    }
    cslul_config_set_message_level(cfg, msglevel);
    return 1;
}

static int set_default_arch(void)
{
    const char *target = getenv("SLUL_TARGET");
    if (target && *target) {
        if (!cslul_config_add_arches(cfg, target)) {
            /* An error is already reported */
            fprintf(stderr, _(
                "Please check the 'SLUL_TARGET' environment variable.\n"));
            return 0;
        }
    } else {
        if (!cslul_config_add_host_arch(cfg)) {
            fprintf(stderr, _("Could not determine output architecture.\n"));
            return 0;
        }
    }
    return 1;
}

/**
 * Converts a positive decimal number in a string to an integer.
 * Unlike strtol, this function does not allow any spaces or +/- sign.
 * Returns 1 if the number is valid, or 0 on error.
 */
static int str2posint(const char *value, int *result)
{
    int r = 0;
    const char *p = value;

    if (!*p) return 0;
    for (;;) {
        char c = *(p++);
        if (!c) break;
        if (c < '0' || c > '9' || r >= INT_MAX/10) return 0;
        r = 10*r + (c - '0');
    }
    *result = r;
    return 1;
}

int main(int argc, char **argv)
{
    int optparse = 1;
    int ok;
    int argleft;
    char *arg, **argp;
    int bad_arg = 0;
    const char *invalid_opt = NULL;
    const char *invalid_opt_value = NULL;
    const char *invalid_outtype = NULL;
    enum CSlulOutputType outtype = CSLUL_OT_AUTO;
    int has_outdir = 0;
    int should_show_version = 0;
    int overridden_ifacedirs = 0;
    int overridden_target = 0;

#ifndef NO_GETTEXT
    setlocale(LC_ALL, "");
    bindtextdomain("cslul", LOCALEDIR);
    textdomain("cslul");
#endif
    progname = argv[0];

    errno = 0;
    cfg = cslul_config_create(NULL);
    if (!cfg) {
        perror(_("Internal error. Cannot start compiler."));
        return EXIT_FAILURE;
    }
    cslul_config_set_message_handler(cfg, &msghandler);
    errout = stderr;
    errout_set = 0;

    /* Parse option arguments (and skip filename arguments) */
    for (argleft = argc-1, argp = argv+1; argleft>0; argleft--, argp++) {
        arg = *argp;
        if (arg[0] == '-') {
            if (arg[1] == '\0' || !optparse) continue; /* stdin/filename argument */
            if (arg[1] == '-') {
                /* Long option */
                if (arg[2] == '\0') { optparse = 0; }
                else if (!strcmp(arg+2, "help")) {
                    show_help();
                    return EXIT_SUCCESS;
                } else if (!strcmp(arg+2, "version")) {
                    should_show_version = 1;
                } else if (!strcmp(arg+2, "no-hints")) {
                    memset(&shown_hint, UCHAR_MAX, sizeof(shown_hint));
                } else if (!strcmp(arg+2, "accept-errors")) {
                    accept_errors = 1;
                } else if (!strncmp(arg+2, "help=", 5) ||
                           !strncmp(arg+2, "version=", 8) ||
                           !strncmp(arg+2, "no-hints=", 9) ||
                           !strncmp(arg+2, "accept-errors=", 14)) {
                    invalid_opt = arg;
                } else {
                    char *value = strchr(arg, '=');
                    int has_equals;
                    if (value) {
                        *value = '\0';
                        value++;
                        has_equals = 1;
                    } else {
                        if (--argleft) {
                            value = *(++argp);
                        } else {
                            value = NULL;
                        }
                        has_equals = 0;
                    }
                    arg += 2;
                    if (!strcmp(arg, "target")) {
                        if (!value) goto missing_arg;
                        /* TODO check for errors? */
                        cslul_config_add_arches(cfg, value);
                        overridden_target = 1;
                    } else if (!strcmp(arg, "outdir")) {
                        if (!check_duplicate_arg(arg, &has_outdir)) continue;
                        if (!value) goto missing_arg;
                        cslul_config_set_output_directory(cfg, value);
                    } else if (!strcmp(arg, "message-level")) {
                        if (!value) goto missing_arg;
                        if (!set_msglevel(value)) {
                            invalid_opt = arg-2;
                            invalid_opt_value = value;
                        }
                    } else if (!strcmp(arg, "error-limit")) {
                        int num;
                        if (!value) goto missing_arg;
                        if (str2posint(value, &num)) {
                            error_limit = errors_left = num;
                        } else {
                            invalid_opt = arg-2;
                            invalid_opt_value = value;
                        }
                    } else if (!strcmp(arg, "error-output")) {
                        FILE *f;
                        if (!value) goto missing_arg;
                        if (*value == '-' && value[1] == '\0') {
                            errout = stdout;
                        } else if ((f = fopen(value, "w")) != NULL) {
                            errout = f;
                            errout_set = 1;
                        } else {
                            perror(value);
                            reported_error = 1;
                        }
                    } else {
                        if (!invalid_opt) invalid_opt = arg-2;
                    }
                    /* Hack to prevent option arguments from being
                       parsed as module filenames. */
                    if (!invalid_opt && !has_equals) arg[-1] = '=';
                }
            } else if (arg[2] != '\0') {
                if (!strcmp(arg, "-help")) {
                    show_help();
                    return EXIT_SUCCESS;
                } else {
                    /* Long option with only one dash (or a combination of
                       multiple short options, but that is not supported) */
                    if (!invalid_opt) invalid_opt = arg;
                }
            } else {
                /* Short option */
                switch (arg[1]) {
                case '?':
                case 'h':
                    show_help();
                    return EXIT_SUCCESS;
                case 'I': {
                    const char *value;
                    if (!--argleft) goto missing_arg;
                    value = *(++argp);
                    if (value[0] == '-' && !value[1]) {
                        overridden_ifacedirs = 1;
                    } else {
                        cslul_config_add_iface_dir(cfg, value);
                    }
                    arg[1] = '=';
                    break; }
                case 'q':
                    cslul_config_set_message_level(cfg, CSLUL_L_ERROR);
                    break;
                case 't': {
                    const char *value;
                    if (!--argleft) goto missing_arg;
                    value = *(++argp);
                    if (!strcmp(value, "auto")) outtype = CSLUL_OT_AUTO;
                    else if (!strcmp(value, "check")) outtype = CSLUL_OT_CHECK;
                    else if (!strcmp(value, "objfile")) outtype = CSLUL_OT_OBJFILE;
                    else if (!strcmp(value, "library")) outtype = CSLUL_OT_LIBRARY;
                    else if (!strcmp(value, "dynlib")) outtype = CSLUL_OT_DYNLIB;
                    else if (!strcmp(value, "statlib")) outtype = CSLUL_OT_STATLIB;
                    else if (!strcmp(value, "header")) outtype = CSLUL_OT_HEADER;
                    else if (!strcmp(value, "plugin")) outtype = CSLUL_OT_PLUGIN;
                    else if (!strcmp(value, "exe")) outtype = CSLUL_OT_EXE;
                    else if (!strcmp(value, "help")) {
                        show_outtype_help();
                        return EXIT_SUCCESS;
                    } else {
                        bad_arg = 1;
                        invalid_outtype = value;
                    }
                    arg[1] = '=';
                    break; }
                case 'V':
                    should_show_version = 1;
                    break;
                default:
                    if (!invalid_opt) invalid_opt = arg;
                }
            }
        }
    }

    if (invalid_opt_value) {
        fprintf(stderr, _("Invalid value '%s' for option '%s'\n"),
                        invalid_opt_value, invalid_opt);
        return 2;
    } else if (invalid_opt) {
        invalid_option(invalid_opt);
        return 2;
    } else if (bad_arg) {
        if (invalid_outtype) {
            fprintf(stderr, _("Invalid output type (-t option): %s\n"
                    "Run '%s -t help' for a list of valid types.\n"),
                    invalid_outtype, progname);
        }
        return 2;
    } else if (reported_error) {
        return 2;
    } else if (should_show_version) {
        show_version();
        return EXIT_SUCCESS;
    }

    if (!overridden_ifacedirs) {
        /* TODO allow default slul-includes directories to be overridden?
        * note that ~/.local/share/slul-interfaces is included by default *
        const char *ifacepath = getenv("SLUL_INTERFACES_PATH");
        ...
        */
        /* TODO related: allow rpath to be overridden in executables built by cslul? */
        if (!cslul_config_add_default_iface_dirs(cfg)) {
            fprintf(stderr, _("Could not determine default search path for interface files.\n"));
            return EXIT_FAILURE;
        }
    }
    if (!overridden_target) {
        if (!set_default_arch()) return EXIT_FAILURE;
    }
    cslul_config_set_output_type(cfg, outtype);
    if (cslul_config_has_errors(cfg)) return EXIT_FAILURE;
    ok = process_modules(argc, argv);
    cslul_config_free(cfg);
    if (errout_set) fclose(errout);

    return ok || accept_errors ? EXIT_SUCCESS : EXIT_FAILURE;
  missing_arg:
    fprintf(stderr, _("%s: option '%s' requires a parameter value\n"), progname, arg);
    return 2;
}