Fix a few minor compiler/standards issues (clang-16 porting) (for main branch)

[val-ms]

Copy of #747 forward-ported for main branch.

In addition, this PR:

• Fixes a few new strict prototype issues.
• Enables these warnings as errors by default at the top level CMake to prevent accidentally introducing more of these in the future.

The description from #747 is as follows...

---

The next major version of clang has threatened to enable some strictness flags by default:

https://bugs.gentoo.org/show_bug.cgi?id=clang-16-porting

Specifically,

• -Werror=implicit-function-declaration
• -Werror=implicit-int
• -Werror=strict-prototypes

Whether or not they all wind up on by default, the problems they catch are easy to fix and usually beneficial for e.g. further compiler diagnostics. Here I've fixed what I had to in order to build v0.103.7.

For the autotools build system, the following autoconf fix (and an autoreconf -fi) is also required:

https://git.savannah.gnu.org/gitweb/?p=autoconf.git;a=commit;h=8b5e2016c7ed2d67f31b03a3d2e361858ff5299b

Otherwise, the checks that are emitted will unduly fail.

[lgtm-com]

This pull request introduces 2 alerts and fixes 1 when merging 74f65ed into 39fbbef - view on LGTM.com

new alerts:

• 2 for Wrong type of arguments to formatting function

fixed alerts:

• 1 for Implicit function declaration

---

Heads-up: LGTM.com's PR analysis will be disabled on the 5th of December, and LGTM.com will be shut down ⏻ completely on the 16th of December 2022. It looks like GitHub code scanning with CodeQL is already set up for this repo, so no further action is needed 🚀. For more information, please check out our post on the GitHub blog.

[val-ms]

@ragusaa I just removed that commit which did this:

diff --git a/CMakeLists.txt b/CMakeLists.txt
index f2c95c35f..74c09bbbb 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -851,6 +851,9 @@ else()
     extract_valid_c_flags(WARNCFLAGS
         -Wall -Wextra
         -Wformat-security
+        -Werror=implicit-function-declaration
+        -Werror=implicit-int
+        -Werror=strict-prototypes
     )
     if(ENABLE_ALL_THE_WARNINGS)
         extract_valid_c_flags(WARNCFLAGS

As discussed, we can figure out how to add this in our CI instead, to prevent introducing new warnings.

[lgtm-com]

This pull request fixes 1 alert when merging c3855e2 into 39fbbef - view on LGTM.com

fixed alerts:

• 1 for Implicit function declaration

---

Heads-up: LGTM.com's PR analysis will be disabled on the 5th of December, and LGTM.com will be shut down ⏻ completely on the 16th of December 2022. It looks like GitHub code scanning with CodeQL is already set up for this repo, so no further action is needed 🚀. For more information, please check out our post on the GitHub blog.

[ragusaa]

This fails to build when running those warnings as errors with clang-14. The two suggestions I have are

1. Add the following to the top of crypto.c
   #if !defined(_WIN32) #define _GNU_SOURCE 1 #endif

2. Change the following line in CMakeLists.txt
   if(CMAKE_COMPILER_IS_GNUCXX)
   to
   if(CMAKE_COMPILER_IS_GNUCXX OR (${CMAKE_CXX_COMPILER_ID} STREQUAL "Clang"))

[val-ms]

This fails to build when running those warnings as errors with clang-14. The two suggestions I have are

1. Add the following to the top of crypto.c
   `#if !defined(_WIN32) #define _GNU_SOURCE 1 #endif`

2. Change the following line in CMakeLists.txt
   `if(CMAKE_COMPILER_IS_GNUCXX)`
   to
   `if(CMAKE_COMPILER_IS_GNUCXX OR (${CMAKE_CXX_COMPILER_ID} STREQUAL "Clang"))`

I went with a variation on the second option. I think it is fixed now.

[lgtm-com]

This pull request fixes 1 alert when merging 9ab74bd into 6ea6ee5 - view on LGTM.com

fixed alerts:

• 1 for Implicit function declaration

---

Heads-up: LGTM.com's PR analysis will be disabled on the 5th of December, and LGTM.com will be shut down ⏻ completely on the 16th of December 2022. It looks like GitHub code scanning with CodeQL is already set up for this repo, so no further action is needed 🚀. For more information, please check out our post on the GitHub blog.