diff options
Diffstat (limited to 'pkgs/build-support/cc-wrapper/setup-hook.sh')
| -rw-r--r-- | pkgs/build-support/cc-wrapper/setup-hook.sh | 135 |
1 files changed, 113 insertions, 22 deletions
diff --git a/pkgs/build-support/cc-wrapper/setup-hook.sh b/pkgs/build-support/cc-wrapper/setup-hook.sh index 104b82425f29..c6abd6281d26 100644 --- a/pkgs/build-support/cc-wrapper/setup-hook.sh +++ b/pkgs/build-support/cc-wrapper/setup-hook.sh @@ -1,51 +1,142 @@ -addCVars () { - if [ -d $1/include ]; then - export NIX_CFLAGS_COMPILE+=" ${ccIncludeFlag:--isystem} $1/include" +# CC Wrapper hygiene +# +# For at least cross compilation, we need to depend on multiple cc-wrappers at +# once---specifically up to one per sort of dependency. This follows from having +# different tools targeting different platforms, and different flags for those +# tools. For example: +# +# # Flags for compiling (whether or not linking) C code for the... +# NIX_BUILD_CFLAGS_COMPILE # ...build platform +# NIX_CFLAGS_COMPILE # ...host platform +# NIX_TARGET_CFLAGS_COMPILE # ...target platform +# +# Notice that these platforms are the 3 *relative* to the package using +# cc-wrapper, not absolute like `x86_64-pc-linux-gnu`. +# +# The simplest solution would be to have separate cc-wrappers per (3 intended +# use-cases * n absolute concrete platforms). For the use-case axis, we would +# @-splice in 'BUILD_' '' 'TARGET_' to use the write environment variables when +# building the cc-wrapper, and likewise prefix the binaries' names so they didn't +# clobber each other on the PATH. But the need for 3x cc-wrappers, along with +# non-standard name prefixes, is annoying and liable to break packages' build +# systems. +# +# Instead, we opt to have just one cc-wrapper per absolute platform. Matching +# convention, the binaries' names can just be prefixed with their target +# platform. On the other hand, that means packages will depend on not just +# multiple cc-wrappers, but the exact same cc-wrapper derivation multiple ways. +# That means the exact same cc-wrapper derivation must be able to avoid +# conflicting with itself, despite the fact that `setup-hook.sh`, the `addCvars` +# function, and `add-flags.sh` are all communicating with each other with +# environment variables. Yuck. +# +# The basic strategy is: +# +# - Everyone exclusively *adds information* to relative-platform-specific +# environment variables, like `NIX_TARGET_CFLAGS_COMPILE`, to communicate +# with the wrapped binaries. +# +# - The wrapped binaries will exclusively *read* cc-wrapper-derivation-specific +# environment variables distinguished with with `infixSalt`, like +# `NIX_@infixSalt@_CFLAGS_COMPILE`. +# +# - `add-flags`, beyond its old task of reading extra flags stuck inside the +# cc-wrapper derivation, will convert the relative-platform-specific +# variables to cc-wrapper-derivation-specific variables. This conversion is +# the only time all but one of the cc-wrapper-derivation-specific variables +# are set. +# +# This ensures the flow of information is exclusive from +# relative-platform-specific variables to cc-wrapper-derivation-specific +# variables. This allows us to support the general case of a many--many relation +# between relative platforms and cc-wrapper derivations. +# +# For more details, read the individual files where the mechanisms used to +# accomplish this will be individually documented. + + +# It's fine that any other cc-wrapper will redefine this. Bash functions close +# over no state, and there's no @-substitutions within, so any redefined +# function is guaranteed to be exactly the same. +ccWrapper_addCVars () { + # The `depOffset` describes how the platforms of the dependencies are slid + # relative to the depending package. It is brought into scope of the + # environment hook defined as the role of the dependency being applied. + case $depOffset in + -1) local role='BUILD_' ;; + 0) local role='' ;; + 1) local role='TARGET_' ;; + *) echo "cc-wrapper: Error: Cannot be used with $depOffset-offset deps, " >2; + return 1 ;; + esac + + if [[ -d "$1/include" ]]; then + export NIX_${role}CFLAGS_COMPILE+=" ${ccIncludeFlag:--isystem} $1/include" fi - if [ -d $1/lib64 -a ! -L $1/lib64 ]; then - export NIX_LDFLAGS+=" -L$1/lib64" + if [[ -d "$1/lib64" && ! -L "$1/lib64" ]]; then + export NIX_${role}LDFLAGS+=" -L$1/lib64" fi - if [ -d $1/lib ]; then - export NIX_LDFLAGS+=" -L$1/lib" + if [[ -d "$1/lib" ]]; then + export NIX_${role}LDFLAGS+=" -L$1/lib" fi - if test -d $1/Library/Frameworks; then - export NIX_CFLAGS_COMPILE="$NIX_CFLAGS_COMPILE -F$1/Library/Frameworks" + if [[ -d "$1/Library/Frameworks" ]]; then + export NIX_${role}CFLAGS_COMPILE+=" -F$1/Library/Frameworks" fi } -envHooks+=(addCVars) +# Since the same cc-wrapper derivation can be depend on in multiple ways, we +# need to accumulate *each* role (i.e. target platform relative the depending +# derivation) in which the cc-wrapper derivation is used. +# `NIX_CC_WRAPPER_@infixSalt@_TARGET_*` tracks this (needs to be an exported env +# var so can't use fancier data structures). +# +# We also need to worry about what role is being added on *this* invocation of +# setup-hook, which `role` tracks. +if [ -n "${crossConfig:-}" ]; then + export NIX_CC_WRAPPER_@infixSalt@_TARGET_BUILD=1 + role="BUILD_" +else + export NIX_CC_WRAPPER_@infixSalt@_TARGET_HOST=1 + role="" +fi + +# Eventually the exact sort of env-hook we create will depend on the role. This +# is because based on what relative platform we are targeting, we use different +# dependencies. +envHooks+=(ccWrapper_addCVars) -# Note: these come *after* $out in the PATH (see setup.sh). +# Note 1: these come *after* $out in the PATH (see setup.sh). +# Note 2: phase separation makes this look useless to shellcheck. +# shellcheck disable=SC2157 if [ -n "@cc@" ]; then addToSearchPath _PATH @cc@/bin fi +# shellcheck disable=SC2157 if [ -n "@binutils_bin@" ]; then addToSearchPath _PATH @binutils_bin@/bin fi +# shellcheck disable=SC2157 if [ -n "@libc_bin@" ]; then addToSearchPath _PATH @libc_bin@/bin fi +# shellcheck disable=SC2157 if [ -n "@coreutils_bin@" ]; then addToSearchPath _PATH @coreutils_bin@/bin fi -if [ -z "$crossConfig" ]; then - ENV_PREFIX="" -else - ENV_PREFIX="BUILD_" -fi +# Export tool environment variables so various build systems use the right ones. -export NIX_${ENV_PREFIX}CC=@out@ +export NIX_${role}CC=@out@ -export ${ENV_PREFIX}CC=@named_cc@ -export ${ENV_PREFIX}CXX=@named_cxx@ +export ${role}CC=@named_cc@ +export ${role}CXX=@named_cxx@ for CMD in \ cpp \ @@ -54,9 +145,9 @@ do if PATH=$_PATH type -p "@binPrefix@$CMD" > /dev/null then - export "${ENV_PREFIX}$(echo "$CMD" | tr "[:lower:]" "[:upper:]")=@binPrefix@${CMD}"; + export "${role}$(echo "$CMD" | tr "[:lower:]" "[:upper:]")=@binPrefix@${CMD}"; fi done -# No local scope available for sourced files -unset ENV_PREFIX +# No local scope in sourced file +unset role |