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LibC: Change putenv (and getenv) to not copy, but directly return the environ values.

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This is in keeping with how putenv should function. It does mean that
the shell's export command now leaks, but that's not a difficult fix.

Contributes to #29.
This commit is contained in:
Robin Burchell 2019-05-16 13:04:47 +02:00 • committed by Andreas Kling
parent c5434e0cfa
commit b2dd12daac
4 changed files with 59 additions and 47 deletions
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88
LibC/stdlib.cpp
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@ -46,18 +46,17 @@ void abort()
char* getenv(const char* name)
{
size_t vl = strlen(name);
for (size_t i = 0; environ[i]; ++i) {
const char* decl = environ[i];
char* eq = strchr(decl, '=');
if (!eq)
continue;
size_t varLength = eq - decl;
char* var = (char*)alloca(varLength + 1);
memcpy(var, decl, varLength);
var[varLength] = '\0';
if (!strcmp(var, name)) {
char* value = eq + 1;
return value;
if (vl != varLength)
continue;
if (strncmp(decl, name, varLength) == 0) {
return eq + 1;
}
}
return nullptr;
@ -65,48 +64,51 @@ char* getenv(const char* name)
int putenv(char* new_var)
{
HashMap<String, String> environment;
char* new_eq = strchr(new_var, '=');
auto handle_environment_entry = [&environment] (const char* decl) {
char* eq = strchr(decl, '=');
if (!eq)
return;
size_t var_length = eq - decl;
char* var = (char*)alloca(var_length + 1);
memcpy(var, decl, var_length);
var[var_length] = '\0';
const char* value = eq + 1;
environment.set(var, value);
};
for (size_t i = 0; environ[i]; ++i)
handle_environment_entry(environ[i]);
handle_environment_entry(new_var);
// FIXME: should remove the var from the environment.
if (!new_eq)
return 0;
//extern bool __environ_is_malloced;
//if (__environ_is_malloced)
// free(environ);
//__environ_is_malloced = true;
auto new_var_len = new_eq - new_var;
size_t environ_size = 0;
for (; environ[environ_size]; ++environ_size) {
char* old_var = environ[environ_size];
char* old_eq = strchr(old_var, '=');
ASSERT(old_eq);
auto old_var_len = old_eq - old_var;
int environment_size = sizeof(char*); // For the null sentinel.
for (auto& it : environment)
environment_size += (int)sizeof(char*) + it.key.length() + 1 + it.value.length() + 1;
if (new_var_len != old_var_len)
continue; // can't match
char* buffer = (char*)malloc(environment_size);
environ = (char**)buffer;
char* bufptr = buffer + sizeof(char*) * (environment.size() + 1);
int i = 0;
for (auto& it : environment) {
environ[i] = bufptr;
memcpy(bufptr, it.key.characters(), it.key.length());
bufptr += it.key.length();
*(bufptr++) = '=';
memcpy(bufptr, it.value.characters(), it.value.length());
bufptr += it.value.length();
*(bufptr++) = '\0';
++i;
if (strncmp(new_var, old_var, new_var_len) == 0) {
environ[environ_size] = new_var;
return 0;
}
}
environ[environment.size()] = nullptr;
// At this point, we need to append the new var.
// 2 here: one for the new var, one for the sentinel value.
char **new_environ = (char**)malloc((environ_size + 2) * sizeof(char*));
if (new_environ == nullptr) {
errno = ENOMEM;
return -1;
}
for (size_t i = 0; environ[i]; ++i) {
new_environ[i] = environ[i];
}
new_environ[environ_size] = new_var;
new_environ[environ_size + 1] = nullptr;
// swap new and old
// note that the initial environ is not heap allocated!
extern bool __environ_is_malloced;
if (__environ_is_malloced)
free(environ);
__environ_is_malloced = true;
environ = new_environ;
return 0;
}