verilog_lint.md

---
---

# `verible-verilog-lint`

Tool for linting Verilog and SystemVerilog code. Part of the Verible tool
suite.

## Command line arguments

```
verible-verilog-lint: usage: /tmp/verible-bin/verible-verilog-lint [options] <file> [<file>...]

  Flags from external/abseil-cpp~/absl/flags/parse.cc:
    --flagfile (comma-separated list of files to load flags from); default: ;
    --fromenv (comma-separated list of flags to set from the environment [use
      'export FLAGS_flag1=value']); default: ;
    --tryfromenv (comma-separated list of flags to try to set from the
      environment if present); default: ;
    --undefok (comma-separated list of flag names that it is okay to specify on
      the command line even if the program does not define a flag with that
      name); default: ;


  Flags from verible/verilog/analysis/verilog-linter.cc:
    --rules (Comma-separated of lint rules to enable. No prefix or a '+' prefix
      enables it, '-' disable it. Configuration values for each rules placed
      after '=' character.); default: ;
    --rules_config (Path to lint rules configuration file. Disables
      --rule_config_search if set.); default: "";
    --rules_config_search (Look for lint rules configuration file
      '.rules.verible_lint' searching upward from the location of each analyzed
      file.); default: false;
    --ruleset ([default|all|none], the base set of rules used by linter);
      default: default;
    --waiver_files (Path to waiver config files (comma-separated). Please refer
      to the README file for information about its format.); default: "";


  Flags from verible/verilog/parser/verilog-parser.cc:
    --verilog_trace_parser (Trace verilog parser); default: false;


  Flags from verible/verilog/tools/lint/verilog-lint.cc:
    --autofix (autofix mode; one of
      [no|patch-interactive|patch|inplace-interactive|inplace|generate-waiver]);
      default: no;
    --autofix_output_file (File to write a patch with autofixes to if
      --autofix=patch or --autofix=patch-interactive or a waiver file if
      --autofix=generate-waiver); default: "";
    --check_syntax (If true, check for lexical and syntax errors, otherwise
      ignore.); default: true;
    --generate_markdown (If true, print the description of every rule formatted
      for the Markdown and exit immediately. Intended for the output to be
      written to a snippet of Markdown.); default: false;
    --help_rules ([all|<rule-name>], print the description of one rule/all rules
      and exit immediately.); default: "";
    --lint_fatal (If true, exit nonzero if linter finds violations.);
      default: true;
    --parse_fatal (If true, exit nonzero if there are any syntax errors.);
      default: true;
    --print_rules_file (Print the current set of lint rules in a format that can
      be used to create a lint rules configuration file (i.e.
      .rules.verible_lint) and exit immediately.); default: false;
    --show_diagnostic_context (prints an additional line on which the diagnostic
      was found,followed by a line with a position marker); default: false;

Try --helpfull to get a list of all flags or --help=substring shows help for
flags which include specified substring in either in the name, or description or
path.
```

## Lint Rules

### always-comb
Checks that there are no occurrences of `always @*`. Use `always_comb` instead. See [Style: combinational-logic].

Enabled by default: true

### always-comb-blocking
Checks that there are no occurrences of non-blocking assignment in combinational logic. See [Style: combinational-logic].

Enabled by default: true

### always-ff-non-blocking
Checks that blocking assignments are, at most, targeting locals in sequential logic. See [Style: sequential-logic].

##### Parameters
  * `catch_modifying_assignments` Default: `false` 
  * `waive_for_locals` Default: `false` 

Enabled by default: true

### banned-declared-name-patterns
Checks for banned declared name against set of unwanted patterns. See [Style: identifiers].

Enabled by default: false

### case-missing-default
Checks that a default case-item is always defined unless the case statement has the `unique` qualifier. See [Style: case-statements].

Enabled by default: true

### constraint-name-style
Check that constraint names follow the required name style specified by a regular expression. See [Style: constraints].

##### Parameter
  * `pattern` Default: `([a-z0-9]+_)+c` 

Enabled by default: true

### create-object-name-match
Checks that the 'name' argument of `type_id::create()` matches the name of the variable to which it is assigned. See [Style: uvm-naming].

Enabled by default: true

### dff-name-style
Checks that D Flip-Flops use appropiate naming conventions in both input and output ports. The left hand side (output) and right hand side (input) are checked against a set of valid suffixes. Additionally, register names might end in a number to denote the pipeline stage index (var_q/var_q1, var_q2, ...). Pipelined signals must get their value from the previous stage: var_q3 <= var_q2. Exceptions to this rule can be configured using a regular expression or waiving whole `if` blocks See [Style: dff-name-style].

##### Parameters
  * `input` Default: `next,n,d` Comma separated list of allowed suffixes for the input port. Suffixes should not include the preceding "_". Empty field means no checks for the input port
  * `output` Default: `reg,r,ff,q` Comma separated list of allowed suffixes for the output port. Should not include the preceding "_". Empty field means no checks for the output port
  * `waive_ifs_with_conditions` Default: `!rst_ni,flush_i,!rst_ni || flush_i,flush_i || !rst_ni` Comma separated list of conditions that will disable the rule inside the `if`s they are evaluated in
  * `waive_lhs_regex` Default: `(?i)mem.*` Nonblocking assigments whose lhs match the regex will not be evaluated

Enabled by default: false

### disable-statement
Checks that there are no occurrences of `disable some_label` if label is referring to a fork or other none sequential block label. Use `disable fork` instead. See [Style: disable-invalid-in-non-sequential].

Enabled by default: false

### endif-comment
Checks that a Verilog `` `endif`` directive is followed by a comment that matches the name of the opening `` `ifdef`` or `` `ifndef``. See [Style: endif-comment].

Enabled by default: false

### enum-name-style
Checks that enum type names follow a naming convention defined by a RE2 regular expression. The default regex pattern expects "lower_snake_case" with either a "_t" or "_e" suffix. Refer to https://github.com/chipsalliance/verible/tree/master/verilog/tools/lint#readme for more detail on verible regex patterns. See [Style: enumerations].

##### Parameter
  * `style_regex` Default: `[a-z_0-9]+(_t|_e)` A regex used to check enum type name style.

Enabled by default: true

### explicit-begin
Checks that a Verilog ``begin`` directive follows all if, else, always, always_comb, always_latch, always_ff, for, forever, foreach, while and initial statements. See [Style: explicit-begin].

##### Parameters
  * `if_enable` Default: `true` All if statements require an explicit begin-end block
  * `else_enable` Default: `true` All else statements require an explicit begin-end block
  * `always_enable` Default: `true` All always statements require an explicit begin-end block
  * `always_comb_enable` Default: `true` All always_comb statements require an explicit begin-end block
  * `always_latch_enable` Default: `true` All always_latch statements require an explicit begin-end block
  * `always_ff_enable` Default: `true` All always_ff statements require an explicit begin-end block
  * `for_enable` Default: `true` All for statements require an explicit begin-end block
  * `forever_enable` Default: `true` All forever statements require an explicit begin-end block
  * `foreach_enable` Default: `true` All foreach statements require an explicit begin-end block
  * `while_enable` Default: `true` All while statements require an explicit begin-end block
  * `initial_enable` Default: `true` All initial statements require an explicit begin-end block

Enabled by default: false

### explicit-function-lifetime
Checks that every function declared outside of a class is declared with an explicit lifetime (static or automatic). See [Style: function-task-explicit-lifetime].

Enabled by default: true

### explicit-function-task-parameter-type
Checks that every function and task parameter is declared with an explicit storage type. See [Style: function-task-argument-types].

Enabled by default: true

### explicit-parameter-storage-type
Checks that every `parameter` and `localparam` is declared with an explicit storage type. See [Style: constants].

##### Parameter
  * `exempt_type` Default: `` Set to `string` to exempt string types

Enabled by default: true

### explicit-task-lifetime
Checks that every task declared outside of a class is declared with an explicit lifetime (static or automatic). See [Style: function-task-explicit-lifetime].

Enabled by default: true

### forbid-consecutive-null-statements
Checks that there are no occurrences of consecutive null statements like `;;` See [Style: redundant-semicolons].

Enabled by default: true

### forbid-defparam
Do not use defparam. See [Style: module-instantiation].

Enabled by default: true

### forbid-line-continuations
Checks that there are no occurrences of `\` when breaking the string literal line. Use concatenation operator with braces instead. See [Style: forbid-line-continuations].

Enabled by default: true

### forbid-negative-array-dim
Check for negative constant literals inside array dimensions. See [Style: forbid-negative-array-dim].

Enabled by default: false

### forbidden-macro
Checks that no forbidden macro calls are used. See [Style: uvm-logging].

Enabled by default: true

### generate-label
Checks that every generate block statement is labeled. See [Style: generate-statements].

Enabled by default: true

### generate-label-prefix
Checks that every generate block label starts with g_ or gen_. See [Style: generate-constructs].

Enabled by default: true

### instance-shadowing
Warns if there are multiple declarations in the same scope that shadow each other with the same name. See [Style: mark-shadowed-instances].

Enabled by default: false

### interface-name-style
Checks that 'interface' names follow a naming convention defined by a RE2 regular expression. The default regex pattern expects "lower_snake_case" with a "_if" or "_e" suffix. Refer to https://github.com/chipsalliance/verible/tree/master/verilog/tools/lint#readme for more detail on regex patterns. See [Style: interface-conventions].

##### Parameter
  * `style_regex` Default: `[a-z_0-9]+(_if)` A regex used to check interface name style.

Enabled by default: true

### invalid-system-task-function
Checks that no forbidden system tasks or functions are used. These consist of the following functions: `$psprintf`, `$random`, and `$dist_*`. As well as non-LRM function `$srandom`. See [Style: forbidden-system-functions].

Enabled by default: true

### legacy-generate-region
Checks that there are no generate regions. See [Style: generate-constructs].

Enabled by default: false

### legacy-genvar-declaration
Checks that there are no separate `genvar` declarations. See [Style: generate-constructs].

Enabled by default: false

### line-length
Checks that all lines do not exceed the maximum allowed length.  See [Style: line-length].

##### Parameter
  * `length` Default: `100` Desired line length

Enabled by default: true

### macro-name-style
Checks that macro names conform to a naming convention defined by a RE2 regular expression. The default regex pattern expects "UPPER_SNAKE_CASE". Exceptions are made for UVM like macros, where macros named 'uvm_*' and 'UVM_*' follow "lower_snake_case" and "UPPER_SNAKE_CASE" naming conventions respectively. Refer to https://github.com/chipsalliance/verible/tree/master/verilog/tools/lint#readme for more detail on verible regex patterns. See [Style: defines].

##### Parameter
  * `style_regex` Default: `[A-Z_0-9]+` A regex used to check macro names style.

Enabled by default: true

### macro-string-concatenation
Concatenation will not be evaluated here. Use `"...`" instead. See [Style: defines].

Enabled by default: false

### mismatched-labels
Check for matching begin/end labels. See [Style: mismatched-labels].

Enabled by default: false

### module-begin-block
Checks that there are no begin-end blocks declared at the module level. See [Style: floating-begin-end-blocks].

Enabled by default: true

### module-filename
If a module is declared, checks that at least one module matches the first dot-delimited component of the file name. Depending on configuration, it is also allowed to replace underscore with dashes in filenames. See [Style: file-names].

##### Parameter
  * `allow-dash-for-underscore` Default: `false` Allow dashes in the filename where there are dashes in the module name

Enabled by default: true

### module-parameter
Checks that module instantiations with more than one parameter are passed in as named parameters, rather than positional parameters. See [Style: module-instantiation].

Enabled by default: true

### module-port
Checks that module instantiations with more than one port are passed in as named ports, rather than positional ports. See [Style: module-instantiation].

Enabled by default: true

### no-tabs
Checks that no tabs are used. Spaces should be used instead of tabs.  See [Style: tabs].

Enabled by default: true

### no-trailing-spaces
Checks that there are no trailing spaces on any lines. See [Style: trailing-spaces].

Enabled by default: true

### numeric-format-string-style
Checks that string literals with numeric format specifiers have proper prefixes for hex and bin values and no prefixes for decimal values. See [Style: number-formatting].

Enabled by default: false

### one-module-per-file
Checks that at most one module is declared per file. See [Style: file-extensions].

Enabled by default: false

### package-filename
Checks that the package name matches the filename. Depending on configuration, it is also allowed to replace underscore with dashes in filenames. See [Style: file-names].

##### Parameter
  * `allow-dash-for-underscore` Default: `false` Allow dashes in the filename corresponding to the underscores in the package

Enabled by default: true

### packed-dimensions-range-ordering
Checks that packed dimension ranges are declare in little-endian (decreasing) order, e.g. `[N-1:0]`. See [Style: packed-ordering].

Enabled by default: true

### parameter-name-style
Checks that parameter and localparm names conform to a naming convention based on a choice of 'CamelCase', 'ALL_CAPS' and a user defined regex ORed together. Empty configurtaion: no style enforcement. Refer to https://github.com/chipsalliance/verible/tree/master/verilog/tools/lint#readme for more detail on verible regex patterns. See [Style: constants].

##### Parameters
  * `localparam_style` Default: `CamelCase` Style of localparam names
  * `parameter_style` Default: `CamelCase|ALL_CAPS` Style of parameter names.
  * `localparam_style_regex` Default: `` A regex used to check localparam name style.
  * `parameter_style_regex` Default: `` A regex used to check parameter name style.

Enabled by default: true

### parameter-type-name-style
Checks that parameter type names follow the lower_snake_case naming convention and end with _t. See [Style: parametrized-objects].

Enabled by default: false

### plusarg-assignment
Checks that plusargs are always assigned a value, by ensuring that plusargs are never accessed using the `$test$plusargs` system task. See [Style: plusarg-value-assignment].

Enabled by default: true

### port-name-suffix
Check that port names end with _i for inputs, _o for outputs and _io for inouts. Alternatively, for active-low signals use _n[io], for differential pairs use _n[io] and _p[io]. See [Style: suffixes-for-signals-and-types].

Enabled by default: false

### positive-meaning-parameter-name
Checks that no parameter name starts with 'disable', using positive naming (starting with 'enable') is recommended. See [Style: binary-parameters].

Enabled by default: true

### posix-eof
Checks that the file ends with a newline. See [Style: posix-file-endings].

Enabled by default: true

### proper-parameter-declaration
Checks that every `parameter` declaration is inside a formal parameter list of modules/classes and every `localparam` declaration is inside a module, class or package. See [Style: constants].

##### Parameters
  * `package_allow_parameter` Default: `false` Allow parameters in packages (treated as a synonym for localparam).
  * `package_allow_localparam` Default: `true` Allow localparams in packages.

Enabled by default: false

### signal-name-style
Checks that signal names conform to a naming convention defined by a RE2 regular expression. Signals are defined as "a net, variable, or port within a SystemVerilog design". The default regex pattern expects "lower_snake_case". Refer to https://github.com/chipsalliance/verible/tree/master/verilog/tools/lint#readme for more detail on verible regex patterns. See [Style: signal-conventions].

##### Parameter
  * `style_regex` Default: `[a-z_0-9]+` A regex used to check signal names style.

Enabled by default: false

### struct-union-name-style
Checks that `struct` and `union` names use lower_snake_case naming convention and end with '_t'. See [Style: struct-union-conventions].

##### Parameter
  * `exceptions` Default: `` Comma separated list of allowed upper-case elements, such as unit-names

Enabled by default: true

### suggest-parentheses
Recommend extra parentheses around subexpressions where it helps readability. See [Style: parentheses].

Enabled by default: true

### suspicious-semicolon
Checks that there are no suspicious semicolons that might affect code behaviour but escape quick visual inspection See [Style: bugprone].

Enabled by default: false

### truncated-numeric-literal
Checks that numeric literals are not longer than their stated bit-width to avoid undesired accidental truncation. See [Style: number-literals].

Enabled by default: true

### typedef-enums
Checks that a Verilog `enum` declaration is named using `typedef`. See [Style: typedef-enums].

Enabled by default: true

### typedef-structs-unions
Checks that a Verilog `struct` or `union` declaration is named using `typedef`. See [Style: typedef-structs-unions].

##### Parameter
  * `allow_anonymous_nested` Default: `false` Allow nested structs/unions to be anonymous.

Enabled by default: true

### undersized-binary-literal
Checks that the digits of binary literals for the configured bases match their declared width, i.e. has enough padding prefix zeros. See [Style: number-literals].

##### Parameters
  * `bin` Default: `true` Checking binary 'b literals.
  * `oct` Default: `false` Checking octal 'o literals.
  * `hex` Default: `false` Checking hexadecimal 'h literals.
  * `lint_zero` Default: `false` Also generate a lint warning for value zero such as `32'h0`; autofix suggestions would be to zero-expand or untype `'0`.
  * `autofix` Default: `true` Provide autofix suggestions, e.g. 32'hAB provides suggested fix 32'h000000AB.

Enabled by default: true

### unpacked-dimensions-range-ordering
Checks that unpacked dimension ranges are declared in big-endian order `[0:N-1]`, and when an unpacked dimension range is zero-based `[0:N-1]`, the size is declared as `[N]` instead. See [Style: unpacked-ordering].

Enabled by default: true

### uvm-macro-semicolon
Checks that no `uvm_* macro calls end with ';'. See [Style: uvm-macro-semicolon-convention].

Enabled by default: false

### v2001-generate-begin
Checks that there are no generate-begin blocks inside a generate region. See [Style: generate-constructs].

Enabled by default: true

### void-cast
Checks that void casts do not contain certain function/method calls.  See [Style: void-casts].

Enabled by default: true


## Version

Generated on 2025-06-04 19:21:36 +0200 from [fb69b42](https://github.com/google/verible/commit/fb69b42d03392c734637576bb347a220b2e9c3ef)