nicolasWDC opened a new issue, #19063:
URL: https://github.com/apache/nuttx/issues/19063
### Description / Steps to reproduce the issue
`include/cxx/ctime` does not import `::localtime` into namespace `std`.
NuttX `time.h` provides `localtime` in the global namespace, but the C++
`<ctime>` shim only imports a subset of the C time API into `std`.
Current `include/cxx/ctime` contains:
```cpp
namespace std
{
using ::time_t;
using ::timer_t;
using ::timespec;
using ::itimerspec;
using ::clock_settime;
using ::clock_gettime;
using ::mktime;
using ::gmtime_r;
using ::gmtime;
using ::strftime;
using ::timer_create;
using ::timer_delete;
using ::timer_settime;
using ::timer_gettime;
using ::timer_getoverrun;
}
```
As a result, valid C++ code using `std::localtime` fails to compile, even
though `::localtime` is available.
## Reproducer
```cpp
#include <ctime>
int test_ctime_symbol()
{
time_t t = 0;
auto *tm = std::localtime(&t);
return tm == nullptr;
}
```
Compile command:
```sh
arm-none-eabi-g++ \
-std=gnu++20 \
-mlittle-endian -march=armv7e-m -mtune=cortex-m4 \
-mfpu=fpv4-sp-d16 -mfloat-abi=hard -mthumb \
-DCONFIG_WCHAR_BUILTIN -D__NuttX__ \
-isystem /build/nuttx/include/cxx \
-isystem /build/nuttx/include \
-c /tmp/test_ctime.cpp -o /tmp/test_ctime.o
```
## Actual behavior
Compilation fails with:
```text
error: 'localtime' is not a member of 'std'; did you mean 'locale'?
```
A real-world failure occurs when building Botan 3.11.1 against the NuttX C++
headers:
```text
src/lib/utils/os_utils/os_utils.cpp: In function 'std::string
Botan::OS::format_time(time_t, const std::string&)':
src/lib/utils/os_utils/os_utils.cpp:355:23: error: 'localtime' is not a
member of 'std'; did you mean 'locale'?
355 | if(auto tmp = std::localtime(&time)) {
| ^~~~~~~~~
| locale
```
## Expected behavior
`std::localtime` should be available after including `<ctime>`, when
`::localtime` is provided by NuttX `time.h`.
The reproducer should compile successfully.
## Suggested fix
Add `using ::localtime;` to `include/cxx/ctime`:
```diff
--- include/cxx/ctime
+++ include/cxx/ctime
@@
using ::clock_settime;
using ::clock_gettime;
using ::mktime;
+ using ::localtime;
using ::gmtime_r;
using ::gmtime;
using ::strftime;
```
## Environment
* NuttX version: 12.13.0
* Target: ARM Cortex-M4 / `xmc4800-relax`
* Toolchain: `arm-none-eabi-g++`
* C++ standard: `gnu++20`
* Configuration:
* `CONFIG_CXX_STANDARD="gnu++20"`
* NuttX C++ headers included through `/build/nuttx/include/cxx`
* NuttX C headers included through `/build/nuttx/include`
## Additional context
This is similar in nature to other C++ shim issues where the C header
exposes a symbol in the global namespace, but the NuttX C++ wrapper does not
import it into namespace `std`.
This issue is independent from the C math wrapper. The `<cmath>` path can
compile successfully, then the build later fails on `<ctime>` because
`std::localtime` is missing.
### On which OS does this issue occur?
[OS: Linux]
### What is the version of your OS?
Ubuntu 22.04
### NuttX Version
12.13.0
### Issue Architecture
[Arch: arm]
### Issue Area
[Area: Posix]
### Host information
_No response_
### Verification
- [x] I have verified before submitting the report.
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