38.15.1.1. Userland objects vs header-only
When factoring out functionality across userland examples, there are two main options:
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use header-only implementations
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use separate C files and link to separate objects.
The downsides of the header-only implementation are:
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slower compilation time, especially for C++
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cannot call C implementations from assembly files
The advantages of header-only implementations are:
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easier to use, just
#includeand you are done, no need to modify build metadata.
As a result, we are currently using the following rule:
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if something is only going to be used from C and not assembly, define it in a header which is easier to use
The slower compilation should be OK as long as split functionality amongst different headers and only include the required ones.
Also we don’t have a choice in the case of C++ template, which must stay in headers.
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if the functionality will be called from assembly, then we don’t have a choice, and must add it to a separate source file and link against it.