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Emulate positive dst for timezones like Dublin #29

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Emulate positive dst for timezones like Dublin #29

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66 changes: 66 additions & 0 deletions src/common.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -545,7 +545,73 @@ void shim::add_math_shimmed_symbols(std::vector<shim::shimmed_symbol> &list) {
});
}

static bool hasNegativeDST() {
tm t;
time_t cur = time(nullptr);
localtime_r(&cur, &t);
time_t before = mktime(&t);
tm a = t;
t.tm_mon += 6;
time_t after = mktime(&t);
tm b = t;
if(a.tm_isdst == !b.tm_isdst) {
auto n0 = a.tm_isdst ? b.tm_gmtoff : a.tm_gmtoff;
auto n1 = b.tm_isdst ? b.tm_gmtoff : a.tm_gmtoff;
return n0 > n1;
}
return false;
}

void shim::add_time_shimmed_symbols(std::vector<shim::shimmed_symbol> &list) {
// fixup timezones like Europe/Dublin by reversing the tm_isdst field of the tm structure
// Microsoft Xbox Authentication Library for android doesn't work with negative DST behavior
if(hasNegativeDST()) {
list.insert(list.end(), {
/* sys/time.h */
{"gettimeofday", gettimeofday},

/* time.h */
{"clock", ::clock},
{"time", ::time},
{"difftime", ::difftime},
{"mktime", &detail::arg_rewrite_helper<decltype(::mktime)>::rewrite<::mktime>},
{"strftime", &detail::arg_rewrite_helper<decltype(::strftime)>::rewrite<::strftime>},
{"strptime", &detail::arg_rewrite_helper<decltype(::strptime)>::rewrite<::strptime>},
{"strftime_l", &detail::arg_rewrite_helper<decltype(::strftime_l)>::rewrite<::strftime_l>},
{"strptime_l", &detail::arg_rewrite_helper<decltype(::strptime_l)>::rewrite<::strptime_l>},
{"gmtime", ::gmtime},
{"gmtime_r", ::gmtime_r},
{"localtime", +[](const time_t* time) {
auto loc = ::localtime(time);
if(!loc) {
return loc;
}
switch(loc->tm_isdst) {
case 1:
loc->tm_isdst = 0;
break;
case 0:
loc->tm_isdst = 1;
break;
default:
break;
}
return loc;
}},
{"localtime_r", &detail::arg_rewrite_helper<decltype(::localtime_r)>::rewrite<::localtime_r>},
{"asctime", &detail::arg_rewrite_helper<decltype(::asctime)>::rewrite<::asctime>},
{"ctime", ::ctime},
{"asctime_r", &detail::arg_rewrite_helper<decltype(::asctime_r)>::rewrite<::asctime_r>},
{"ctime_r", ::ctime_r},
{"tzname", ::tzname},
{"tzset", ::tzset},
{"daylight", &::daylight},
{"timezone", &::timezone},
{"nanosleep", ::nanosleep},
{"clock_gettime", clock_gettime},
});
return;
}
list.insert(list.end(), {
/* sys/time.h */
{"gettimeofday", gettimeofday},
Expand Down
53 changes: 53 additions & 0 deletions src/common.h
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Original file line number Diff line number Diff line change
Expand Up @@ -6,6 +6,7 @@
#include "argrewrite.h"
#include "mallinfo.h"
#include <stdarg.h>
#include <ctime>

namespace shim {

Expand Down Expand Up @@ -176,4 +177,56 @@ namespace shim {

void add_socket_shimmed_symbols(std::vector<shim::shimmed_symbol> &list);

namespace detail {

template <class T>
struct tm_detail {
tm loc;
using source = T;

source before(source src) {
if(src) {
loc = *src;
switch(loc.tm_isdst) {
case 1:
loc.tm_isdst = 0;
break;
case 0:
loc.tm_isdst = 1;
break;
default:
break;
}
return &loc;
}
return nullptr;
}
void after(const tm* src) {

}

void after(tm* src) {
if(src) {
switch(loc.tm_isdst) {
case 1:
loc.tm_isdst = 0;
break;
case 0:
loc.tm_isdst = 1;
break;
default:
break;
}
*src = loc;
}
}
};

template <>
struct arg_rewrite<tm *> : tm_detail<tm*> {};
template <>
struct arg_rewrite<const tm *> : tm_detail<const tm*> {};

}

}
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