Const char array in function call

Development
1

I stumbled on a little “trick”, or rather something in the C language I did not know was possible.

    uint8_t cmd[2] = {0x24, 0x00}; // Single shot measurement command

    if (i2c_write(SHT3X_ADDRESS, cmd, sizeof(cmd))) {
        return; // Error writing to the sensor
    }

In the past I put e.g. I2C data into an array, and then included the array in the function call.

    if (i2c_write(SHT3X_ADDRESS, (uint8_t[]){0x24, 0x00}, 2)) {
        return; // Error writing to the sensor
    }

I learned the constant character data can be packed directly into the function call like this, which I think is much easier to write and read.

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2

I think that’s a neat hack.
Non-standard coding practices feel cool.

However, this does have some downsides:

  • No symbolic name for that array, so debugger can’t show it to you.
  • sizeof(byte_array) is not possible, so you have to manually update the size … making copy/paste errors more likely.

Perhaps something along the following lines:

static const uint8_t cmd[] = {0x24, 0x00};
if (i2c_write(SHT3X_ADDRESS, cmd, sizeof(cmd))) {
    // ...

By excluding the size of the command array, copy/paste errors are less likely. Even better, give the array a better name, and put the commands all up in a single location:

static const uint8_t CMD_SINGLE_SHOT_MEASURE[] = { 0x24, 0x00 };
static const uint8_t CMD_SOMETHING_ELSE[]  = { ... };

Then the code is almost documents itself.

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3

Yeah, you’re right, this is much cleaner for writing drivers.

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