If I am going to spend the time considering a new programming language, I also have to spend the time seeing what last little drops I can squeeze out of VB6.
Over the years there have been a number of projects that intercept the VB compiling and linking process which is handled by external exes from the main IDE. These come in several flavors with different capabilities.
Some allow for the inclusion of inline asm and C code which is held in commented out blocks in the vb source files. Some link in external obj modules. And still some others allow you to tweak the linker settings according to a basic script so that you can create standard Dlls and export functions for use in other languages like C.
With VB6 not as popular as it was, some of these projects have fallen off of the web, or at least take some real hunting to locate anymore. I have found a handful of noteworthy ones and am mirroring them below.
The one I like the best so far, is the vbLinkTool project which I have created a sample for. I will probably also update it some more to add the ability to link in C Obj files.
Its small and clean and does not require a vb adding that hooks the build process in the IDE itself (debugging nightmare). Instead if just replaces the default link.exe and proxies calls to the real link after tweaking the command line.
Personally i rather compile my C Obj modules separate and link them in latter, instead of relying on complex code running in the IDE to extract comments, assemble/compile and then link for me. To much going on to go wrong, and plugins are to annoying to debug. (plus potential stability issues that could cause loss of source code changes).