Cleanup clang compiler warnings

[anjohnson]

After these changes there's only one build warning left from pva2pva builds with Clang 15.0 on macOS, a deprecation warning for epicsThreadExitMain() which I deliberately left in. I removed the other deprecation warnings because they are in test files that apparently check the deprecated API.

I had to update the .ci module to various targets to build, but I didn't get around to removing the CentOS-7 build so that still dies.

[AppVeyorBot]

❌ Build pva2pva 1.0.48 failed (commit 2f1548b337 by @anjohnson)

[AppVeyorBot]

❌ Build pva2pva 1.0.51 failed (commit 2f1548b337 by @anjohnson)

[anjohnson]

It looks like the ci update that I did may need some Appveyor config changes; any advice on that would be welcome (I haven't checked the ci-scripts release notes yet). The vs2019 builds all fail immediately like this, but both vs2015 and vs2017 builds succeed:

Build started
git config --global core.autocrlf true
git clone -q --depth=50 https://github.com/epics-base/pva[2](https://ci.appveyor.com/project/mdavidsaver/pva2pva/builds/50365445/job/a7npfywh2mocqfq5#L2)pva.git C:\projects\pva2pva
git fetch -q origin +refs/pull/6[3](https://ci.appveyor.com/project/mdavidsaver/pva2pva/builds/50365445/job/a7npfywh2mocqfq5#L3)/merge:
git checkout -qf FETCH_HEAD
Restoring build cache
Cache 'C:\Users\appveyor\.tools' - Restored
Running Install scripts
cinst re2c
'cinst' is not recognized as an internal or external command,
operable program or batch file.
Command exited with code 1
Get-ChildItem *.tap -Recurse -Force | % { Push-AppveyorArtifact $_.FullName -FileName $_.Name }
python .ci/cue.py build test-results -s
python: can't open file 'C:\\projects\\pva2pva\\.ci\\cue.py': [Errno 2] No such file or directory
Command exited with code 2

[ralphlange]

cinst is the Chocolatey installer.

By all means, that should be available on the GHA Windows runners.

[AppVeyorBot]

❌ Build pva2pva 1.0.49 failed (commit ef9cdb0951 by @anjohnson)

[AppVeyorBot]

❌ Build pva2pva 1.0.52 failed (commit ef9cdb0951 by @anjohnson)

[AppVeyorBot]

✅ Build pva2pva 1.0.53 completed (commit 8f91792199 by @anjohnson)

[AppVeyorBot]

✅ Build pva2pva 1.0.50 completed (commit 8f91792199 by @anjohnson)

[anjohnson]

I think this PR is ready to go now, unless we also want to suppress the deprecation warning for the epicsThreadExitMain() call in softIocPVA's main() function.

[mdavidsaver]

How is this causing a warning?

Anonymous namespaces date to C++98. This is the c++ equivalent of static functions, also effecting special symbols for classes.

[mdavidsaver]

Strictly speaking symbols in an anonymous namespace were not specified to have internal linkage until c++11, but in practice clang, gcc, and msvc have done so for many years.

[anjohnson]

Right, they're supported but annoyingly warned about:

../gwmain.cpp:245:57: warning: non-type template argument referring to function 'iocsh_drop' with internal linkage is a C++11 extension [-Wc++11-extensions]
        epics::iocshRegister<const char*, const char*, &iocsh_drop>("drop", "client", "channel");
                                                        ^~~~~~~~~~
../gwmain.cpp:205:6: note: non-type template argument refers to function here
void iocsh_drop(const char *client, const char *channel)
     ^

This PR is about cleaning up compiler warnings, and on macOS with Clang-15 I'm getting several of the above from both gwmain.cpp and qsrv.cpp.

An alternative approach would be to turn off those c++11-extensions warnings, preferably in the Base build configuration files. The following local PoC works for me, but it would have to be compiler-specific, maybe even dependent on the GCC & Clang versions:

diff --git a/p2pApp/Makefile b/p2pApp/Makefile
index 602518b..6a27152 100644
--- a/p2pApp/Makefile
+++ b/p2pApp/Makefile
@@ -6,6 +6,7 @@ include $(TOP)/configure/CONFIG
 #=============================
 
 USR_CPPFLAGS += -I$(TOP)/common
+USR_CXXFLAGS += -Wno-c++11-extensions
 
 PROD_HOST = p2p