Fix undefined behavior in callback functions' parameter passing

[mrannanj]

There is undefined behavior in how the callback functions arg_resetfn, arg_scanfn, arg_checkfn, and arg_errorfn are used currently. The original type of those functions has the parent type as void*, but the actual function implementations have the void* parent as something like struct arg_date* parent, but they are cast to the function type with void* parent. This is apparently undefined behavior, and the clang undefined behavior sanitizer catches this.

So, to see the errors, use this change to CMakeLists.txt:

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 67cee27..f267a19 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -69,6 +69,9 @@ if(ARGTABLE3_ENABLE_CONAN AND EXISTS "${CMAKE_BINARY_DIR}/conanbuildinfo.cmake")
   set(CMAKE_EXE_LINKER_FLAGS "${CMAKE_EXE_LINKER_FLAGS} -Wl,-rpath-link,${LINK_FLAGS}")
 endif()
 
+add_compile_options("-fsanitize=undefined")
+add_link_options("-fsanitize=undefined")
+
 set(ARGTABLE3_AMALGAMATION_SRC_FILE ${PROJECT_SOURCE_DIR}/dist/argtable3.c)
 set(ARGTABLE3_SRC_FILES
   ${PROJECT_SOURCE_DIR}/src/arg_cmd.c

The errors will looks like:

./tests/test_amalgamation 
/home/martti/gh/argtable3/dist/argtable3.c:5374:13: runtime error: call to function arg_lit_resetfn through pointer to incorrect function type 'void (*)(void *)'
/home/martti/gh/argtable3/dist/argtable3.c:3378: note: arg_lit_resetfn defined here
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /home/martti/gh/argtable3/dist/argtable3.c:5374:13 
/home/martti/gh/argtable3/dist/argtable3.c:5227:37: runtime error: call to function arg_lit_scanfn through pointer to incorrect function type 'int (*)(void *, const char *)'
/home/martti/gh/argtable3/dist/argtable3.c:3383: note: arg_lit_scanfn defined here
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /home/martti/gh/argtable3/dist/argtable3.c:5227:37 
/home/martti/gh/argtable3/dist/argtable3.c:5361:29: runtime error: call to function arg_lit_checkfn through pointer to incorrect function type 'int (*)(void *)'
/home/martti/gh/argtable3/dist/argtable3.c:3394: note: arg_lit_checkfn defined here
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /home/martti/gh/argtable3/dist/argtable3.c:5361:29 
/home/martti/gh/argtable3/dist/argtable3.c:5270:41: runtime error: call to function arg_lit_scanfn through pointer to incorrect function type 'int (*)(void *, const char *)'
/home/martti/gh/argtable3/dist/argtable3.c:3383: note: arg_lit_scanfn defined here
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /home/martti/gh/argtable3/dist/argtable3.c:5270:41 
/home/martti/gh/argtable3/dist/argtable3.c:5319:21: runtime error: call to function arg_int_scanfn through pointer to incorrect function type 'int (*)(void *, const char *)'
/home/martti/gh/argtable3/dist/argtable3.c:3187: note: arg_int_scanfn defined here
SUMMARY: UndefinedBehaviorSanitizer: undefined-behavior /home/martti/gh/argtable3/dist/argtable3.c:5319:21 

[tomghuang]

@mrannanj : Really appreciate that you found this function prototype mismatch issue. I'm going to merge it. However, I just found that the actions/upload-artifact@v3 has been deprecated and we need to upgrade to actions/upload-artifact@v4 in the GitHub workflow. This is why the CI checks failed.

I've merged a patch to fix this GitHub action issue on the master branch. Could you please rebase your feature branch on the latest master and then push it again? Otherwise, I don't know how to make this pull request pass the CI checks. Thanks.