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execlineb: change execlineb wrapper to C script

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Instead of using execlineb to define the execlineb wrapper, we replace
it by a little C wrapper.

This is mainly done because on non-Linux systems (i.e. mainly macOS),
it is impossible for a shebang interpreter to be itself a shebang
script.
It is, however, perfectly fine to have a chain that goes
shebang -> ELF -> shebang -> ELF -> …

Co-Authored-By: Laurent Bercot <ska-skaware@skarnet.org>
This commit is contained in:
Profpatsch 2019-10-18 21:30:59 +02:00
parent d2c9469ef7
commit fc62890f2d
2 changed files with 61 additions and 23 deletions
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41
pkgs/tools/misc/execline/default.nix
View File

@ -1,6 +1,6 @@
{ lib, skawarePackages { lib, skawarePackages
# for execlineb-with-builtins # for execlineb-with-builtins
, coreutils, gnugrep, writeScriptBin, runCommand , coreutils, gnugrep, writeScriptBin, runCommand, runCommandCC
# Whether to wrap bin/execlineb to have the execline tools on its PATH. # Whether to wrap bin/execlineb to have the execline tools on its PATH.
, execlineb-with-builtins ? true , execlineb-with-builtins ? true
}: }:
@ -43,29 +43,24 @@ let
}; };
# a wrapper around execlineb, which provides all execline # A wrapper around execlineb, which provides all execline
# tools on `execlineb`’s PATH. # tools on `execlineb`’s PATH.
execlineb-with-builtins-drv = # It is implemented as a C script, because on non-Linux,
let eldir = "${execline}/bin"; # nested shebang lines are not supported.
in writeScriptBin "execlineb" '' execlineb-with-builtins-drv = runCommandCC "execlineb" {} ''
#!${eldir}/execlineb -s0 mkdir -p $out/bin
# appends the execlineb bin dir to PATH if not yet in PATH cc \
${eldir}/define eldir ${eldir} -O \
''${eldir}/ifelse -Wall -Wpedantic \
{ -D 'EXECLINEB_PATH()="${execline}/bin/execlineb"' \
# since this is nix, we can grep for the execline drv hash in PATH -D 'EXECLINE_BIN_PATH()="${execline}/bin"' \
# to see whether it’s already in there -I "${skalibs.dev}/include" \
''${eldir}/pipeline -L "${skalibs.lib}/lib" \
{ ${coreutils}/bin/printenv PATH } -l"skarnet" \
${gnugrep}/bin/grep --quiet "${eldir}" -o "$out/bin/execlineb" \
} ${./execlineb-wrapper.c}
# it’s there already '';
{ ''${eldir}/execlineb $@ }
# not there yet, add it
''${eldir}/importas oldpath PATH
''${eldir}/export PATH "''${eldir}:''${oldpath}"
''${eldir}/execlineb $@
'';
# the original execline package, with bin/execlineb overwritten # the original execline package, with bin/execlineb overwritten
execline-with-builtins = runCommand "my-execline" execline-with-builtins = runCommand "my-execline"

43
pkgs/tools/misc/execline/execlineb-wrapper.c Normal file
View File

@ -0,0 +1,43 @@
#include <stdlib.h>
#include <string.h>
#include <skalibs/stralloc.h>
#include <skalibs/djbunix.h>
#include <skalibs/strerr2.h>
#include <skalibs/env.h>
#define dienomem() strerr_diefu1sys(111, "stralloc_catb")
// macros from outside
/* const char* EXECLINEB_PATH; */
/* const char* EXECLINE_BIN_PATH; */
int main(int argc, char const* argv[], char const *const *envp)
{
PROG = "execlineb-wrapper";
char const* path = getenv("PATH");
stralloc path_modif = STRALLOC_ZERO;
// modify PATH if unset or EXECLINEB_BIN_PATH is not yet there
if ( !path || ! strstr(path, EXECLINE_BIN_PATH())) {
// prepend our execline path
if ( ! stralloc_cats(&path_modif, "PATH=")
|| ! stralloc_cats(&path_modif, EXECLINE_BIN_PATH()) ) dienomem();
// old path was not empty
if ( path && path[0] ) {
if ( ! stralloc_catb(&path_modif, ":", 1)
|| ! stralloc_cats(&path_modif, path) ) dienomem();
}
// append final \0
if ( ! stralloc_0(&path_modif) ) dienomem();
}
// exec into execlineb and append path_modif to the environment
xpathexec_r_name(
EXECLINEB_PATH(),
argv,
envp, env_len(envp),
path_modif.s, path_modif.len
);
}