llvm/llvm-project

Create bugprone-printf-array check

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#40,511 opened on Mar 21, 2019

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bugzillacheck-requestclang-tidygood first issue

Description
Bugzilla Link 41166
Version unspecified
OS All

Extended Description

It's a common idiom to have a fixed-size buffer of characters allocated on the stack and then to printf into the buffer. Create a check that recommends that the counted versions of functions are used, e.g. prefer snprintf over sprintf.

Example:

void f()
{
  char buff[80];
  sprintf(buff, "Hello, %s!\n", "world");
}

Becomes:

void f()
{
  char buff[80];
  snprintf(buff, sizeof(buff), "Hello, %s!\n", "world");
}

Contributor guide

Tech stack
cpp
Domain
toolingdeveloper experience
Issue type
feature
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
1-2 days
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
fresh
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
clear
Prerequisites
C programmingclang tidy frameworkAST matchers
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
45
Research direction
First, examine existing clang tidy checks in the llvm project repository under clang tools extra/clang tidy/ to understand the structure (e.g., check class, register check, add documentation). The new check should be placed in the bugprone module. Use AST matchers to find calls to sprintf where the first argument is a fixed size char array (use arrayType() and hasType() matchers). Then emit a diagnostic recommending snprintf with sizeof. Look at similar checks like bugprone sprintf return value for reference. No linked PRs or maintainer questions are present, so the implementation is open. Test cases should be added under clang tools extra/test/clang tidy/.