wine-proxy.c: helper for Debian's wine-unstable

/*
compile:
  WINE_SUFFIX=-unstable
  WINE_PROXY=wine${WINE_SUFFIX}
  gcc -std=c11 -O3 -g0 wine-proxy.c -ldpkg -o ${WINE_PROXY} -DSUFFIX=${WINE_SUFFIX}
  sudo install ${WINE_PROXY} /usr/bin
*/

#define _GNU_SOURCE

#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>

#include <sys/types.h>
#include <sys/stat.h>

#define LIBDPKG_VOLATILE_API

#include <dpkg/arch.h> // libdpkg-dev

// --------------------------
// configuration
// --------------------------

#ifndef SUFFIX
// #define WINE_SUFFIX "-unstable"
#define WINE_SUFFIX ""
#else
/*
 two-pass stringification according to
 http://gcc.gnu.org/onlinedocs/cpp/Stringification.html
*/
#define S0(a) #a
#define S1(a) S0(a)
#define WINE_SUFFIX S1(SUFFIX)
#endif

#ifndef WINE_FULLNAME
#define WINE_FULLNAME "wine"WINE_SUFFIX
#endif

#ifndef WINE_BINDIR
#define WINE_BINDIR "/usr/lib/"WINE_FULLNAME
#endif

#ifndef WINE32
#define WINE32 WINE_BINDIR"/wine"
#endif

#ifndef WINE64
#define WINE64 WINE_BINDIR"/wine64"
#endif

// --------------------------

#define TRUE 1
#define FALSE 0
#define TEST(a,b) (((a)&(b))==(b))

void echo(const char * string) {
    printf("%s\n", string);
}

void env_default(const char * name, const char * value) {
    char * curr = getenv(name);

    if ((curr != NULL) && (strlen(curr) > 0)) {
        return;
    }

    setenv(name, value, TRUE);
}

int is_binary(char * path) {
    int file;
    struct stat file_stat;

    file = open(path, O_NOATIME | O_NOCTTY | O_PATH, O_ACCMODE);
    if (file == -1) { return FALSE; }

    while (TRUE) {
        if (0 != fstat(file, &file_stat)) { break; }
        if (!S_ISREG(file_stat.st_mode)) { break; }
        if (!TEST(file_stat.st_mode, S_IROTH | S_IXOTH)) { break; }

        close(file);

        return TRUE;
    }

    return FALSE;
}

// never returns if succeed
int try_exec(char * binary_path, char ** argv, char ** env) {
    int file = open(binary_path, O_NOATIME | O_NOCTTY | O_CLOEXEC, O_RDONLY);
    if (file == -1) { return 1; }

    int result = fexecve(file, argv, env);

    close(file);

    return result;
}

// --------------------------

char * wine32 = WINE32;
char * wine64 = WINE64;

extern char ** environ;

// --------------------------

int main(int argc, char ** argv) {
    char * wine = NULL;

    if (is_binary(wine32)) {
        wine = wine32;
    } else if (is_binary(wine64)) {
        wine = wine64;

        struct dpkg_arch * a_amd64 = dpkg_arch_find("amd64");
        struct dpkg_arch * a_i386 = dpkg_arch_find("i386");

        if (
            (a_amd64->type == DPKG_ARCH_NATIVE)
            &&
            (a_i386->type != DPKG_ARCH_FOREIGN)
        ) {
            echo("It looks like multiarch needs to be enabled!");
            echo("As root, please execute following:");
            echo("    dpkg --add-architecture i386 && apt-get install wine32"WINE_SUFFIX);
        }
    } else {
        echo("error: unable to find wine executable. this shouldn't happen.");
        return 1;
    }

    env_default("WINELOADER", wine);
    env_default("WINEDEBUG", "-all");

    argv[0] = wine;

    // return try_exec(wine, argv, environ);
    return execve(wine, argv, environ);
}