llvm/llvm-project

c11: Accepts ill-formed program with inline function definition containing modifiable variable with static storage duration.

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#39,524 opened on Dec 28, 2018

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bugzillacclang:diagnosticsconfirmedgood first issue

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Description
Bugzilla Link 40177
Version trunk
OS All
CC @hfinkel,@zygoloid

Extended Description

Test case (prog.c):

inline void f() { static int x; }

int main() { }

Compilation command line:

clang prog.c -Wall -Wextra -std=c11 -pedantic-errors

Observed behaviour:

No error message outputed. Only a warning message outputed.

Expected behaviour:

An error message outputed.

The program violates 6.7.4/3:

"An inline definition of a function with external linkage shall not contain
 a definition of a modifiable object with static or thread storage duration,
 and shall not contain a reference to an identifier with internal linkage."

Since -pedantic-errors is used we should get an error instead of a warning.

Note:

GCC gives the expected error message.

Contributor guide

Research direction
Locate the warning for inline function with static local variable in clang's source (likely in SemaDecl.cpp). Change the diagnostic from warning to error when pedantic errors is enabled.
Tech stack
c
Domain
tooling
Issue type
Bug
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.
Half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
Active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
Clear
Prerequisites
C
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30