#2897: HsFFI.h is not in the default include path for hsc2hs
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Reporter: cjs | Owner:
Type: bug | Status: new
Priority: highest | Milestone: 7.4.1
Component: hsc2hs | Version: 6.10.1
Resolution: | Keywords:
Testcase: | Blockedby:
Difficulty: Unknown | Os: Unknown/Multiple
Blocking: | Architecture: Unknown/Multiple
Failure: None/Unknown |
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Comment(by duncan):
I suggest we go back to having the standard template `#include HsFFI.h`
first.
The point is:
* hsc2hs is a generic tool that can be used for different Haskell
implementations
* The output of hsc2hs is however not independent of the Haskell
implementation. This is because each Haskell implementation has its own C
environment, and hsc2hs must use that same environment or it will produce
incorrect results.
* The HsFFI.h is a reasonable way for each Haskell implementation to set
up its C environment.
Therefore, when using hsc2hs, the user (or build tool) needs to tell
hsc2hs which Haskell implementation they are using, by pointing hsc2hs to
that implementation's HsFFI.h file.
So running `hsc2hs foo.hsc` on it's own ''should'' fail. That is the right
thing to do. There is not enough information from that invocation to
produce correct results. It should not guess, that will also produce
incorrect results.
However it should fail in a comprehensible way and provide the user with
an easy way to do the basic thing:
1. search the given -I dirs for HsFFI.h.
2. if it's not found, complain that the user needs to tell it which
Haskell implementation to use (because the results depend on the C
environment of that implementation). Tell the user they can either specify
the -I dir for their impl, or they can use the --ghc `flag`.
3. if the `--ghc` flag is given, hsc2hs calls `ghc-pkg field rts include-
dirs`, using the `ghc-pkg` on the $PATH, to find the include dir for
HsFFI.h. No support for other ghc instances/versions, just the one on the
$PATH. All non-trivial uses should work by specifying the appropriate -I
dir for the Haskell impl instance.
This combination means that people who really want to invoke hsc2hs
manually can do so by giving the --ghc flag. Everyone else can continue to
have other build tools call hsc2hs, and pass in the appropriate -I flags
for the Haskell impl that they are using. This makes it a relatively
lightweight solution, hsc2hs doesn't need to know much about lots of
different Haskell implementations, just enough to satisfy casual users.
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2897#comment:16>
GHC <http://www.haskell.org/ghc/>
The Glasgow Haskell Compiler
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