@Chris-Kawa Thanks for the input.
"That's horrible. Both the fact you're using PATH for that and the reason for it." - I'd be happy to learn a better way.
"a build step that copies dependencies to your output directory" - I don't know what this means or how to accomplish it. In general, I have control over where the output directory is and what goes into it but I don't understand putting "dependencies" in it.
I broadly understand static vs dynamic linking, but certainly do not many fine details. For the bulk of libraries I create, I just make the .a with no affiliated .dll. One of my big confusions is why the relevant info is not available through whatever mechanism it always has been. For the immediate situation, the .a and .dll are in the same location, and I think the compile process specifies that location. Not sure what you mean by "mapped directories". Mapped where and by whom?
The sources are where they were at compile time. I have, and have always, copied the created libraries to a general library location. that is somehow magically found when some app is ultimately executed. All of the libraries under question were built by me from source with the same set of tools.
I don't know how to make the debugger load debug info and I apparently don't know where it looks for sources. I have monkeyed around with the path mapping feature, but apparently not yet in a useful way
for reference, below is an extract from the transcript for the build process for this library showing the exact compiler and linker options. Below that is a comparable transcript from building another of my libraries. The second library is rather heavily used and regularly part of a debugging session.
\usr\local\MinGW-w64\x86_64-7.2.0-posix-seh-rt_v5-rev1\mingw64\bin\g++ -c -MT debug/zzzzsomefile.o -MMD -MP -MF debug.d/zzzzsomefile.Td -g -fno-keep-inline-dllexport -Og -std=c++1z -fno-exceptions -Wall -W -Wextra -Wvla -Wdate-time -Wshift-overflow=2 -Wduplicated-cond -Wno-stringop-overflow -DUNICODE -D_UNICODE -DWIN32 -DMINGW_HAS_SECURE_API=1 -DWINVER=0x0601 -D_WIN32_WINNT=0x0601 -DQT_NO_NARROWING_CONVERSIONS_IN_CONNECT -DQT_BUILD_zzzz_LIB -DQT_BUILDING_QT -D_CRT_SECURE_NO_WARNINGS -D_USE_MATH_DEFINES -DQT_NO_CAST_TO_ASCII -DQT_ASCII_CAST_WARNINGS -DQT_MOC_COMPAT -DQT_USE_QSTRINGBUILDER -DQT_DEPRECATED_WARNINGS -DQT_DISABLE_DEPRECATED_BEFORE=0x040800 -DQT_NO_EXCEPTIONS -DQT_QML_DEBUG -DQT_GUI_LIB -DQT_CORE_LIB -I. -isystem C:\usr\local\Qt\Qt-5.12_x86_64-7.2.0-posix-seh-rt_v5-rev1\include -isystem C:\usr\local\Qt\Qt-5.12_x86_64-7.2.0-posix-seh-rt_v5-rev1\include\QtGui\5.12.0 -isystem C:\usr\local\Qt\Qt-5.12_x86_64-7.2.0-posix-seh-rt_v5-rev1\include\QtGui\5.12.0\QtGui -isystem C:\usr\local\Qt\Qt-5.12_x86_64-7.2.0-posix-seh-rt_v5-rev1\include\QtGui -isystem C:\usr\local\Qt\Qt-5.12_x86_64-7.2.0-posix-seh-rt_v5-rev1\include\QtCore\5.12.0 -isystem C:\usr\local\Qt\Qt-5.12_x86_64-7.2.0-posix-seh-rt_v5-rev1\include\QtCore\5.12.0\QtCore -isystem C:\usr\local\Qt\Qt-5.12_x86_64-7.2.0-posix-seh-rt_v5-rev1\include\QtCore -isystem \usr\local\Boost\boost_1_69_0\include\boost_1_69 -o debug/zzzzsomefile.o zzzzsomefile.cpp
\usr\local\MinGW-w64\x86_64-7.2.0-posix-seh-rt_v5-rev1\mingw64\bin\g++ -Wl,-s -shared -Wl,-subsystem,windows -Wl,--out-implib,debug/libzzzzzzzd.a -o debug/zzzzzzzd.dll long list of .o files -LC:\usr\local\Qt\Qt-5.12_x86_64-7.2.0-posix-seh-rt_v5-rev1\lib C:\usr\local\Qt\Qt-5.12_x86_64-7.2.0-posix-seh-rt_v5-rev1\lib\libQt5Gui.a C:\usr\local\Qt\Qt-5.12_x86_64-7.2.0-posix-seh-rt_v5-rev1\lib\libQt5Core.a debug/zzzzzzzd_resource_rec.o -lglu32 -lopengl32 -lgdi32 -luser32
copy debug\libzzzzzzzd.a \users\owner\documents\mike\src\lib\x86_64-7.2.0-posix-seh-rt_v5-rev1\gcc_dll
copy debug\zzzzzzzd.dll \users\owner\documents\mike\src\lib\x86_64-7.2.0-posix-seh-rt_v5-rev1\gcc_dll
\usr\local\MinGW-w64\x86_64-7.2.0-posix-seh-rt_v5-rev1\mingw64\bin\g++ -c -MT debug/myLogWindow.o -MMD -MP -MF debug.d/myLogWindow.Td -g -fno-keep-inline-dllexport -O0 -std=gnu++11 -Wall -W -Wextra -fexceptions -mthreads -DUNICODE -D_UNICODE -DWIN32 -DQT_QML_DEBUG -DQT_WIDGETS_LIB -DQT_GUI_LIB -DQT_CORE_LIB -DQT_NEEDS_QMAIN -I. -I\users\owner\documents\mike\src\include -isystem C:\usr\local\Qt\Qt-5.12_x86_64-7.2.0-posix-seh-rt_v5-rev1\include -isystem C:\usr\local\Qt\Qt-5.12_x86_64-7.2.0-posix-seh-rt_v5-rev1/mkspecs\win32-g++ -isystem C:\usr\local\Qt\Qt-5.12_x86_64-7.2.0-posix-seh-rt_v5-rev1\include\QtWidgets -isystem C:\usr\local\Qt\Qt-5.12_x86_64-7.2.0-posix-seh-rt_v5-rev1\include\QtGui -isystem C:\usr\local\Qt\Qt-5.12_x86_64-7.2.0-posix-seh-rt_v5-rev1\include\QtCore -isystem \usr\local\Boost\boost_1_69_0\include\boost_1_69 -o debug/myLogWindow.o myLogWindow.cpp
ar -ruv debug/libmyqtlibd.a debug/myLogWindow.o *****long list of .o files *****
copy debug\libmyqtlibd.a \users\owner\documents\mike\src\lib\x86_64-7.2.0-posix-seh-rt_v5-rev1\gcc_dll\libmyqtlibd.a