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1ac5398589
I hate the thing too even though I made it, and rather just get rid of it. But we can't do that yet. In the meantime, this brings us more inline with autoconf and will make it slightly easier for me to write a pkg-config wrapper, which we need.
121 lines
4.6 KiB
Bash
121 lines
4.6 KiB
Bash
# CC Wrapper hygiene
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#
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# For at least cross compilation, we need to depend on multiple cc-wrappers at
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# once---specifically up to one per sort of dependency. This follows from having
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# different tools targeting different platforms, and different flags for those
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# tools. For example:
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#
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# # Flags for compiling (whether or not linking) C code for the...
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# NIX_CFLAGS_COMPILE_FOR_BUILD # ...build platform
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# NIX_CFLAGS_COMPILE # ...host platform
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# NIX_CFLAGS_COMPILE_FOR_TARGET # ...target platform
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#
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# Notice that these platforms are the 3 *relative* to the package using
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# cc-wrapper, not absolute like `x86_64-pc-linux-gnu`.
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#
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# The simplest solution would be to have separate cc-wrappers per (3 intended
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# use-cases * n absolute concrete platforms). For the use-case axis, we would
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# @-splice in 'BUILD_' '' 'TARGET_' to use the write environment variables when
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# building the cc-wrapper, and likewise prefix the binaries' names so they didn't
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# clobber each other on the PATH. But the need for 3x cc-wrappers, along with
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# non-standard name prefixes, is annoying and liable to break packages' build
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# systems.
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#
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# Instead, we opt to have just one cc-wrapper per absolute platform. Matching
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# convention, the binaries' names can just be prefixed with their target
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# platform. On the other hand, that means packages will depend on not just
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# multiple cc-wrappers, but the exact same cc-wrapper derivation multiple ways.
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# That means the exact same cc-wrapper derivation must be able to avoid
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# conflicting with itself, despite the fact that `setup-hook.sh`, the `addCvars`
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# function, and `add-flags.sh` are all communicating with each other with
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# environment variables. Yuck.
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#
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# The basic strategy is:
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#
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# - Everyone exclusively *adds information* to relative-platform-specific
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# environment variables, like `NIX_CFLAGS_COMPILE_FOR_TARGET`, to communicate
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# with the wrapped binaries.
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#
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# - The wrapped binaries will exclusively *read* cc-wrapper-derivation-specific
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# environment variables distinguished with with `suffixSalt`, like
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# `NIX_CFLAGS_COMPILE_@suffixSalt@`.
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#
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# - `add-flags`, beyond its old task of reading extra flags stuck inside the
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# cc-wrapper derivation, will convert the relative-platform-specific
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# variables to cc-wrapper-derivation-specific variables. This conversion is
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# the only time all but one of the cc-wrapper-derivation-specific variables
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# are set.
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#
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# This ensures the flow of information is exclusive from
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# relative-platform-specific variables to cc-wrapper-derivation-specific
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# variables. This allows us to support the general case of a many--many relation
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# between relative platforms and cc-wrapper derivations.
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#
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# For more details, read the individual files where the mechanisms used to
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# accomplish this will be individually documented.
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# Skip setup hook if we're neither a build-time dep, nor, temporarily, doing a
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# native compile.
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#
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# TODO(@Ericson2314): No native exception
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[[ -z ${strictDeps-} ]] || (( "$hostOffset" < 0 )) || return 0
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# It's fine that any other cc-wrapper will redefine this. Bash functions close
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# over no state, and there's no @-substitutions within, so any redefined
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# function is guaranteed to be exactly the same.
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ccWrapper_addCVars () {
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# See ../setup-hooks/role.bash
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local role_post
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getHostRoleEnvHook
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if [ -d "$1/include" ]; then
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export NIX_CFLAGS_COMPILE${role_post}+=" -isystem $1/include"
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fi
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if [ -d "$1/Library/Frameworks" ]; then
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export NIX_CFLAGS_COMPILE${role_post}+=" -iframework $1/Library/Frameworks"
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fi
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}
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# See ../setup-hooks/role.bash
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getTargetRole
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getTargetRoleWrapper
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# We use the `targetOffset` to choose the right env hook to accumulate the right
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# sort of deps (those with that offset).
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addEnvHooks "$targetOffset" ccWrapper_addCVars
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# Note 1: these come *after* $out in the PATH (see setup.sh).
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# Note 2: phase separation makes this look useless to shellcheck.
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# shellcheck disable=SC2157
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if [ -n "@cc@" ]; then
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addToSearchPath _PATH @cc@/bin
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fi
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# shellcheck disable=SC2157
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if [ -n "@libc_bin@" ]; then
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addToSearchPath _PATH @libc_bin@/bin
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fi
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# shellcheck disable=SC2157
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if [ -n "@coreutils_bin@" ]; then
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addToSearchPath _PATH @coreutils_bin@/bin
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fi
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# Export tool environment variables so various build systems use the right ones.
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export NIX_CC${role_post}=@out@
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export CC${role_post}=@named_cc@
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export CXX${role_post}=@named_cxx@
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export CC${role_post}=@named_cc@
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export CXX${role_post}=@named_cxx@
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# If unset, assume the default hardening flags.
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: ${NIX_HARDENING_ENABLE="fortify stackprotector pic strictoverflow format relro bindnow"}
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export NIX_HARDENING_ENABLE
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# No local scope in sourced file
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unset -v role_post
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