What kind of issue is this?

• PlatformIO Core.
  If you’ve found a bug, please provide an information below.

You can erase any parts of this template not applicable to your Issue.

Configuration

Operating system: Win 10 x64

PlatformIO Version (platformio --version): 6.0.2a2

Description of problem

The PlatformIO core does not extract -D<macro> definitions from CCFLAGS into the e.g. VSCode Intellisense c_cpp_properties.json. Only macros in CPPDEFINES are.

Steps to Reproduce

1. Create a new Nodemcuv2 + Arduino (ESP8266) project
2. Add a call to tzset(); in setup()

Actual Results

Intellisense does not know about this function and highlights it as error.

Expected Results

Intellisense knows about this function since Arduino.h is included which includes time.h which says

#if __POSIX_VISIBLE
void      tzset 	(void);
#endif

If problems with PlatformIO Build System:

The content of platformio.ini:

[env:d1_mini]
platform = espressif8266
board = d1_mini
framework = arduino

Source file to reproduce issue:

#include <Arduino.h>
#include <string.h>
#include <string>

void setup() {}
void loop()
{
    const char *s = "test";
    char buf[64];
    strlcpy(buf, s, sizeof(buf));

    setenv("TZ", "CST-8", 1);
    tzset();

    int res = strcasecmp("A", "a");
}

Additional info

Intellisense does not recognize tzset() because that needs the _GNU_SOURCE to be defined (which through a specific chain enables POSIX_VISIBLE). The Arduino-ESP8266 build process activates that macro through CCFLAGS here and it correctly shows up in the build commands. However, the .vscode/c_cpp_properties.json does not have _GNU_SOURCE in the defines section because -D flags in CCFLAGS is not considered during the generation of this file.

I considered this fixing this by moving -D flags from CCFLAGS to CPPDEFINES, but this is then specific to Arduino-ESP8266. I think in general it would be good if the core is able to recognize this situation and relays the activated macros to the IDEs correctly. (See esp8266/Arduino#8579).

Also see community topic here and here.