I share the frustration the author describes. When I started out programming as a child, I used Turbo Pascal, but I was aware of Turbo C and that more people used that than Pascal. Nevertheless, I couldn't really wrap my head around C at the time, and it was partly due to linker errors that I couldn't understand; and it seemed that Turbo Pascal just didn't use a linker, so it was easier to understand and tinker with at age 9.
It's intriguing to think how different my experience could have been if educational material at the time had focused as much on full explanations of the compiler+linker process, including example error conditions, as it did on teaching the language.
30 years later, I like to claim that I have a reasonably workable understanding of how compilers work, but I'm still nebulous on how linkers do what they do. I'm much more comfortable with higher-level compilers such as C# that compile to a VM bytecode (IL) and don't worry about linkers.
virgilp · 23m ago
Linkers pretty much map data sections to memory, and in doing so are able to replace symbolic names (like global variables, or goto targets) with numbers. They may also completely drop some things that are not needed (e.g. code/files in a library that is never referenced).
I'm over-simplifying and also it's a bit incorrect, because there's also the loader that does a lot of the same work that linkers do, when loading the program in memory. So linkers don't actually produce the final image - but really, they're rather "simple" things (for some definition of "simple").
The hard-to-understand linker errors are typically caused by the compiler, not the linker (it's the compiler that speculatively chooses to use a symbol with a long and funny name, thinking that it'll later be provided by <somebody>, when in fact the linker later finds out that no library or object file actually provided said symbol; and then for the linker to give you a decent error message, it needs to have a pretty good understanding of what the compiler was actually trying to do - i.e. to know implementation details of the compiler that otherwise would not concern it at all).
stef-13013 · 20m ago
Really nice, thanks !!
lynx97 · 4h ago
Nitpick: Almost all Hello World C examples are wrong. printf is for when you need to use a format string. Hello World doesn't. Besides:
> puts() writes the string s and a trailing newline to stdout.
int main() { puts("Hello World!"); }
PhilipRoman · 4h ago
Eh, it compiles down to the same thing with optimizations enabled:
But I agree, using printf for constant strings is one step away from doing printf(x) which is a big no-no.
Joker_vD · 4h ago
Useless bit of compiler optimizations trivia: the "this printf() is equivalent to puts()" optimization seems to work by looking for the '%' in the format string, not by counting whether there is only one argument to printf(), e.g. if you add 42 as a second argument to the printf() — which is absolutely legal and required by the standard to Work as Intended™ — the resulting binary still uses puts().
unwind · 3h ago
I agree, but I have to point out that if you're gonna be like that, then you should be explicit about your final
It's intriguing to think how different my experience could have been if educational material at the time had focused as much on full explanations of the compiler+linker process, including example error conditions, as it did on teaching the language.
30 years later, I like to claim that I have a reasonably workable understanding of how compilers work, but I'm still nebulous on how linkers do what they do. I'm much more comfortable with higher-level compilers such as C# that compile to a VM bytecode (IL) and don't worry about linkers.
I'm over-simplifying and also it's a bit incorrect, because there's also the loader that does a lot of the same work that linkers do, when loading the program in memory. So linkers don't actually produce the final image - but really, they're rather "simple" things (for some definition of "simple").
The hard-to-understand linker errors are typically caused by the compiler, not the linker (it's the compiler that speculatively chooses to use a symbol with a long and funny name, thinking that it'll later be provided by <somebody>, when in fact the linker later finds out that no library or object file actually provided said symbol; and then for the linker to give you a decent error message, it needs to have a pretty good understanding of what the compiler was actually trying to do - i.e. to know implementation details of the compiler that otherwise would not concern it at all).
> puts() writes the string s and a trailing newline to stdout.
int main() { puts("Hello World!"); }
https://godbolt.org/z/zcqa4Txen
But I agree, using printf for constant strings is one step away from doing printf(x) which is a big no-no.