Missing '-Wreturn-type' warning for 'main' having no return statement in C89 mode

[morinmorin]

Bugzilla Link	21276
Version	unspecified
OS	All

Extended Description

Clang does not emit "control reaches end of non-void function [-Wreturn-type]" warning for 'main' having no return statement in C89 mode (-std=c89, gnu89).

Clang adds implicit-return-zero in C89 mode. But, since the C89 standard does not require it, wouldn't it be better to emit warning?

[cor3ntin]

@Sirraide @AaronBallman

[llvmbot]

@llvm/issue-subscribers-c

Author: Masaki Moriguchi (a.k.a. Michel Morin) (morinmorin)

| | | | --- | --- | | Bugzilla Link | [21276](https://llvm.org/bz21276) | | Version | unspecified | | OS | All |

Extended Description

Clang does not emit "control reaches end of non-void function [-Wreturn-type]" warning for 'main' having no return statement in C89 mode (-std=c89, gnu89).

Clang adds implicit-return-zero in C89 mode. But, since the C89 standard does not require it, wouldn't it be better to emit warning?

[AaronBallman]

Agreed, this should be given a diagnostic under -pedantic in C89 mode.

[llvmbot]

Hi!

This issue may be a good introductory issue for people new to working on LLVM. If you would like to work on this issue, your first steps are:

1. Check that no other contributor has already been assigned to this issue. If you believe that no one is actually working on it despite an assignment, ping the person. After one week without a response, the assignee may be changed.
2. In the comments of this issue, request for it to be assigned to you, or just create a pull request after following the steps below. Mention this issue in the description of the pull request.
3. Fix the issue locally.
4. Run the test suite locally. Remember that the subdirectories under test/ create fine-grained testing targets, so you can e.g. use make check-clang-ast to only run Clang's AST tests.
5. Create a Git commit.
6. Run git clang-format HEAD~1 to format your changes.
7. Open a pull request to the upstream repository on GitHub. Detailed instructions can be found in GitHub's documentation. Mention this issue in the description of the pull request.

If you have any further questions about this issue, don't hesitate to ask via a comment in the thread below.

[llvmbot]

@llvm/issue-subscribers-good-first-issue

Author: Masaki Moriguchi (a.k.a. Michel Morin) (morinmorin)

| | | | --- | --- | | Bugzilla Link | [21276](https://llvm.org/bz21276) | | Version | unspecified | | OS | All |

Extended Description

Clang does not emit "control reaches end of non-void function [-Wreturn-type]" warning for 'main' having no return statement in C89 mode (-std=c89, gnu89).

Clang adds implicit-return-zero in C89 mode. But, since the C89 standard does not require it, wouldn't it be better to emit warning?