All local variables, function parameters, struct fields should be camelCase.

[luckytyphlosion]

Useful grep to find instances:
grep -Pwr --include="*.c" --include="*.h" "[a-z_]+_[a-z_]+[,;\)]" --exclude-dir="tools" --exclude-dir="sub" --exclude-dir="lib" --exclude-dir=".github" --exclude-dir="files"

Do not apply this logic to Nintendo Libraries.

Local variable example

Good:

void String_RadioAddStatic(String *string, u8 level) {
    u32 width3Dots = FontID_GetGlyphWidth(0, CHAR_ELLIPSIS);
    u32 width1Dot = FontID_GetGlyphWidth(0, CHAR_ONE_DOT);
    u32 width2Dots = FontID_GetGlyphWidth(0, CHAR_TWO_DOTS);
    u32 curWidth;
    int strLen;
    int i;

	// rest of function omitted
}

Bad:

void String_RadioAddStatic(String *string, u8 level) {
    u32 width_3dots = FontID_GetGlyphWidth(0, CHAR_ELLIPSIS);
    u32 width_1dot = FontID_GetGlyphWidth(0, CHAR_ONE_DOT);
    u32 width_2dots = FontID_GetGlyphWidth(0, CHAR_TWO_DOTS);
    u32 cur_width;
    int str_len;
    int i;

	// rest of function omitted
}

Function parameter example

Good:

int TrainerData_GetAttr(u32 trIdx, TrainerAttr attrNo);

Bad:

int TrainerData_GetAttr(u32 tr_idx, TrainerAttr attr_no);

Struct field example

Good:

typedef struct MailMessage {
    u16 msgBank; // camelCase
    u16 msgNo;
    u16 fields[MAILMSG_FIELDS_MAX];
} MailMessage;

Bad:

typedef struct MailMessage {
    u16 msg_bank; // snake_case
    u16 msg_no;
    u16 fields[MAILMSG_FIELDS_MAX];
} MailMessage;

Exception: unknown fields. There is no consensus whether unk fields should have an underscore between the unk and the offset value (and probably other stuff)

• Case 1: underscore

struct HiddenItemData {
    u16 itemId;
    u8 quantity;
    u8 unk_3;
    u16 unk_4;
    u16 index;
};

• Case 2: no underscore

struct HiddenItemData {
    u16 itemId;
    u8 quantity;
    u8 unk3;
    u16 unk4;
    u16 index;
};

[AnonymousRandomPerson]

I don't see a reason to include underscores in the unk vars if nothing else has them.

[red031000]

imo no underscore in unknown fields, again this is already in the style guide, I just haven't gone through and fixed it all yet

[PikalaxALT]

Hi, snakehead (Python programmer) here. snake_case is beautiful and any attempts to eliminate it will be met with Protean Arceus.

[adrienntindall]

imo no underscore in unknown fields, again this is already in the style guide, I just haven't gone through and fixed it all yet

I use underscore in BattleContext to differentiate it from unknowns in BattleSystem since it's much easier to control and replace that way without conflicts lol

[luckytyphlosion]

imo no underscore in unknown fields, again this is already in the style guide, I just haven't gone through and fixed it all yet

I use underscore in BattleContext to differentiate it from unknowns in BattleSystem since it's much easier to control and replace that way without conflicts lol

That sounds like you need a better way of distinguishing the fields.

[adrienntindall]

imo no underscore in unknown fields, again this is already in the style guide, I just haven't gone through and fixed it all yet

I use underscore in BattleContext to differentiate it from unknowns in BattleSystem since it's much easier to control and replace that way without conflicts lol

That sounds like you need a better way of distinguishing the fields.

No like I would cntrl + f and replace the unkowns constantly and it was much easier to do so when I wasn't accidently replacing the wrong unkA40 or whatever

[luckytyphlosion]

yes so do something like unk_z_A40 or something

[tgsm]

I personally prefer snake_case, no underscores in unknown variables/members

[AsparagusEduardo]

I prefer camelCase in general, though I feel it would be useful to have unknown fields to stand out with a different style specifically to make people document them.

[luckytyphlosion]

On the record:

Donnel — Today at 10:10 PM
I’m for camelCase
Lhea — Today at 10:10 PM
I'm for camelCase (ignore that I haven't worked on pokeplatinum lately)