Describe the bug
The cast between unrelated types (as the one shown below) is not safe when the sizes of unsigned and time_t are different:
unsigned int ts_cast = ts;
struct tm *tm_cast = gmtime((time_t*) &ts_cast)
On our target system the sizes of the two types happened to be the same when using the -m32 compiler option but differ for -m64
This case was found in StRoot/StDaqLib/SSD/SSD_Reader.cxx due to the failed test 24. The log from the job. More specifically,
bfc.C(20, "P2005,tofDat,logger,MakeEvent,ITTF,ssddat,spt,SsdIt,SvtIt,pmdRaw,OShortR,OSpaceZ2", "/star/rcf/test/daq/2005/048/st_physics_6048025_raw_1020002.daq")
To Reproduce
Here is a small program to demonstrate the problem:
#include <ctime>
#include <iostream>
#include <vector>
using namespace std;
int main ()
{
// $ date -d @1108647599
// Thu Feb 17 08:39:59 EST 2005
cout << "sizeof(unsigned): " << sizeof(unsigned) << '\n';
cout << "sizeof(time_t): " << sizeof(time_t) << '\n';
for (int ts : vector<int>{0, 5*24*3600+33, 1108647599})
{
time_t ts_nocast = ts;
struct tm *tm_nocast = gmtime(&ts_nocast);
unsigned int ts_cast = ts;
struct tm *tm_cast = gmtime((time_t*) &ts_cast);
cout << "tm_cast: " << asctime(tm_cast);
cout << "tm_nocast: " << asctime(tm_nocast);
}
return 0;The erroneous output can be seen when comparing the -m32 and -m64 options respectively:
https://godbolt.org/z/xs9oezxro
https://godbolt.org/z/h3M5Pvq7f
Expected behavior
gmtime should return a valid date for the given Unix time when compiled with either -m32 or -m64 options
PS Many thanks to @veprbl for private discussion
Describe the bug
The cast between unrelated types (as the one shown below) is not safe when the sizes of
unsignedandtime_tare different:On our target system the sizes of the two types happened to be the same when using the -m32 compiler option but differ for -m64
This case was found in
StRoot/StDaqLib/SSD/SSD_Reader.cxxdue to the failed test 24. The log from the job. More specifically,To Reproduce
Here is a small program to demonstrate the problem:
The erroneous output can be seen when comparing the -m32 and -m64 options respectively:
https://godbolt.org/z/xs9oezxro
https://godbolt.org/z/h3M5Pvq7f
Expected behavior
gmtime should return a valid date for the given Unix time when compiled with either -m32 or -m64 options
PS Many thanks to @veprbl for private discussion