win32env.c

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/*-------------------------------------------------------------------------
 *
 * win32env.c
 *    putenv(), setenv(), and unsetenv() for win32.
 *
 * These functions update both the process environment and caches in
 * (potentially multiple) C run-time library (CRT) versions.
 *
 * Portions Copyright (c) 1996-2024, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *
 * IDENTIFICATION
 *    src/port/win32env.c
 *
 *-------------------------------------------------------------------------
 */
 
#include "c.h"
 
 
/*
 * Note that unlike POSIX putenv(), this doesn't use the passed-in string
 * as permanent storage.
 */
int
pgwin32_putenv(const char *envval)
{
    char       *envcpy;
    char       *cp;
    typedef int (_cdecl * PUTENVPROC) (const char *);
    static const char *const modulenames[] = {
        "msvcrt",               /* Visual Studio 6.0 / MinGW */
        "msvcrtd",
        "msvcr70",              /* Visual Studio 2002 */
        "msvcr70d",
        "msvcr71",              /* Visual Studio 2003 */
        "msvcr71d",
        "msvcr80",              /* Visual Studio 2005 */
        "msvcr80d",
        "msvcr90",              /* Visual Studio 2008 */
        "msvcr90d",
        "msvcr100",             /* Visual Studio 2010 */
        "msvcr100d",
        "msvcr110",             /* Visual Studio 2012 */
        "msvcr110d",
        "msvcr120",             /* Visual Studio 2013 */
        "msvcr120d",
        "ucrtbase",             /* Visual Studio 2015 and later */
        "ucrtbased",
        NULL
    };
    int         i;
 
    /*
     * Update process environment, making this change visible to child
     * processes and to CRTs initializing in the future.  Do this before the
     * _putenv() loop, for the benefit of any CRT that initializes during this
     * pgwin32_putenv() execution, after the loop checks that CRT.
     *
     * Need a copy of the string so we can modify it.
     */
    envcpy = strdup(envval);
    if (!envcpy)
        return -1;
    cp = strchr(envcpy, '=');
    if (cp == NULL)
    {
        free(envcpy);
        return -1;
    }
    *cp = '\0';
    cp++;
    if (*cp)
    {
        /*
         * Only call SetEnvironmentVariable() when we are adding a variable,
         * not when removing it. Calling it on both crashes on at least
         * certain versions of MinGW.
         */
        if (!SetEnvironmentVariable(envcpy, cp))
        {
            free(envcpy);
            return -1;
        }
    }
    free(envcpy);
 
    /*
     * Each CRT has its own _putenv() symbol and copy of the environment.
     * Update the environment in each CRT module currently loaded, so every
     * third-party library sees this change regardless of the CRT it links
     * against.  Addresses within these modules may become invalid the moment
     * we call FreeLibrary(), so don't cache them.
     */
    for (i = 0; modulenames[i]; i++)
    {
        HMODULE     hmodule = NULL;
        BOOL        res = GetModuleHandleEx(0, modulenames[i], &hmodule);
 
        if (res != 0 && hmodule != NULL)
        {
            PUTENVPROC  putenvFunc;
 
            putenvFunc = (PUTENVPROC) (pg_funcptr_t) GetProcAddress(hmodule, "_putenv");
            if (putenvFunc)
                putenvFunc(envval);
            FreeLibrary(hmodule);
        }
    }
 
    /*
     * Finally, update our "own" cache.  This is redundant with the loop
     * above, except when PostgreSQL itself links to a CRT not listed above.
     * Ideally, the loop does visit all possible CRTs, making this redundant.
     */
    return _putenv(envval);
}
 
int
pgwin32_setenv(const char *name, const char *value, int overwrite)
{
    int         res;
    char       *envstr;
 
    /* Error conditions, per POSIX */
    if (name == NULL || name[0] == '\0' || strchr(name, '=') != NULL ||
        value == NULL)
    {
        errno = EINVAL;
        return -1;
    }
 
    /* No work if variable exists and we're not to replace it */
    if (overwrite == 0 && getenv(name) != NULL)
        return 0;
 
    envstr = (char *) malloc(strlen(name) + strlen(value) + 2);
    if (!envstr)                /* not much we can do if no memory */
        return -1;
 
    sprintf(envstr, "%s=%s", name, value);
 
    res = pgwin32_putenv(envstr);
    free(envstr);
    return res;
}
 
int
pgwin32_unsetenv(const char *name)
{
    int         res;
    char       *envbuf;
 
    envbuf = (char *) malloc(strlen(name) + 2);
    if (!envbuf)
        return -1;
 
    sprintf(envbuf, "%s=", name);
    res = pgwin32_putenv(envbuf);
    free(envbuf);
    return res;
}