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tool_homedir: Change GetEnv() to use libcurl's curl_getenv()

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- Deduplicate GetEnv() code.

- On Windows change ultimate call to use Windows API
  GetEnvironmentVariable() instead of C runtime getenv().

Prior to this change both libcurl and the tool had their own GetEnv
which over time diverged. Now the tool's GetEnv is a wrapper around
curl_getenv (libcurl API function which is itself a wrapper around
libcurl's GetEnv).

Furthermore this change fixes a bug in that Windows API
GetEnvironmentVariable() is called instead of C runtime getenv() to get
the environment variable since some changes aren't always visible to the
latter.

Reported-by: Christoph M. Becker

Fixes https://github.com/curl/curl/issues/4774
Closes https://github.com/curl/curl/pull/4863
This commit is contained in:
Jay Satiro 2020-01-29 03:23:55 -05:00
parent 39d5621cbd
commit 9dc350b60c
2 changed files with 58 additions and 42 deletions
Download patch file Download diff file Expand all files Collapse all files

45
lib/getenv.c
View file

@ -27,25 +27,48 @@
#include "memdebug.h"
static
char *GetEnv(const char *variable)
static char *GetEnv(const char *variable)
{
#if defined(_WIN32_WCE) || defined(CURL_WINDOWS_APP)
(void)variable;
return NULL;
#else
#ifdef WIN32
char env[4096];
char *temp = getenv(variable);
env[0] = '\0';
if(temp != NULL)
ExpandEnvironmentStringsA(temp, env, sizeof(env));
return (env[0] != '\0')?strdup(env):NULL;
#elif defined(WIN32)
/* This uses Windows API instead of C runtime getenv() to get the environment
variable since some changes aren't always visible to the latter. #4774 */
char *buf = NULL;
char *tmp;
DWORD bufsize;
DWORD rc = 1;
const DWORD max = 32768; /* max env var size from MSCRT source */
for(;;) {
tmp = realloc(buf, rc);
if(!tmp) {
free(buf);
return NULL;
}
buf = tmp;
bufsize = rc;
/* It's possible for rc to be 0 if the variable was found but empty.
Since getenv doesn't make that distinction we ignore it as well. */
rc = GetEnvironmentVariableA(variable, buf, bufsize);
if(!rc || rc == bufsize || rc > max) {
free(buf);
return NULL;
}
/* if rc < bufsize then rc is bytes written not including null */
if(rc < bufsize)
return buf;
/* else rc is bytes needed, try again */
}
#else
char *env = getenv(variable);
return (env && env[0])?strdup(env):NULL;
#endif
#endif
}
char *curl_getenv(const char *v)