...
| Code Block |
|---|
|
int main(int argc, char const *argv[], char const *envp[]) {
size_t i;
if (setenv("MY_NEW_VAR", "new_value", 1);) != 0) {
/* Handle Error */
}
if (envp != NULL) {
for (i = 0; envp[i] != NULL; i++) {
puts(envp[i]);
}
}
return 0;
}
|
...
| Code Block |
|---|
|
extern char **environ;
/* ... */
int main(int argc, char const *argv[]) {
size_t i;
if (setenv("MY_NEW_VAR", "new_value", 1); != 0) {
/* Handle Error */
}
if (environ != NULL) {
for (i = 0; environ[i] != NULL; i++) {
puts(environ[i]);
}
}
return 0;
}
|
Non-Compliant Code Example (Windows)
After a call to the Windows _putenv_s() function, or other function that modifies the environment, the envp pointer may no longer reference the environment.
| Code Block |
|---|
|
int main(int argc, char const *argv[], char const *envp[]) {
size_t i;
if (_putenv_s("MY_NEW_VAR", "new_value", 1) != 0) {
/* Handle Error */
}
if (envp != NULL) {
for (i = 0; envp[i] != NULL; i++) {
puts(envp[i]);
}
}
return 0;
}
|
Because envp no longer points to the current environment, this program has undefined behavior.
Compliant Solution (Windows)
Use _environ in place of envp when defined.
| Code Block |
|---|
|
_CRTIMP extern char **_environ;
/* ... */
int main(int argc, char const *argv[]) {
size_t i;
if (_putenv_s("MY_NEW_VAR", "new_value", 1);) != 0) {
/* Handle Error */
}
if (_environ != NULL) {
for (i = 0; _environ[i] != NULL; i++) {
puts(_environ[i]);
}
}
return 0;
}
|
...
| Wiki Markup |
|---|
\[[ISO/IEC 9899:1999|AA. C References#ISO/IEC 9899-1999]\] Section J.5.1, "Environment Arguments"
\[[MSDN|AA. C References#MSDN]\] [{{getenv, _wgetenv}}|http://msdn.microsoft.com/en-us/library/tehxacec.aspx], [{{_environ, _wenviron}}|http://msdn.microsoft.com/en-us/library/stxk41x1.aspx], [{{_putenv_s, _wputenv_s}}|http://msdn.microsoft.com/en-us/library/eyw7eyfw.aspx]
\[[Open Group 04|AA. C References#Open Group 04]\] [{{setenv()}}|http://www.opengroup.org/onlinepubs/009695399/functions/setenv.html] |
...
