#!/bin/bash
# Try compiling sources against various C compiler + standard combinations.

set -euo pipefail

cpu_count=$(cat /proc/cpuinfo | grep "^processor" | wc -l)

# Use files listed on command line, if specified.
file_pattern=*.c
if [[ $#ARGV > 1 ]]; then
   file_pattern=$@
fi

# Get list of files that require sys headers.  These won't compile with MingW.
declare -A require_sys
for f in $(grep -l "#include.*sys/" $file_pattern /dev/null); do
   require_sys[$f]=1
done

# Warning settings.
silences="-Wno-implicit-fallthrough"
warnings="-Wall -Wextra -Werror -pedantic $silences"

# Initialize options for each compiler we want to test.
#
# Besides flags related to compiler warnings, we need the "-I." to add current
# directory to the include path.  This is so that "#include __FILE__" would
# work even if the input source files are accessed with relative path.
declare -A cflags
cflags[gcc]="$warnings -I."
cflags[clang]="$warnings -I."
cflags[x86_64-w64-mingw32-gcc]="$warnings -I."

# Need -Wno-deprecated for clang++ because it doesn't want to compile C files
# as C++.
declare -A cppflags
cppflags[g++]="$warnings -I."
cppflags[clang++]="$warnings -Wno-deprecated -I."
cppflags[x86_64-w64-mingw32-g++]="$warnings -I."

# Generate commands for each C compiler+standard combination.
commands=$(mktemp)
found_compilers=0
for cc in ${!cflags[@]}; do
   # Only include command of the compiler can report its own version.
   #
   # This is so that we skip compilers that are not installed.
   if ! ( $cc --version > /dev/null 2>&1 ); then
      continue
   fi
   found_compilers=1

   for input in $file_pattern; do
      if [[ ! -s $input ]]; then
         continue
      fi

      # Add commands for each standard plus GNU extensions.
      for std in {c,gnu}{89,99,11,17}; do
         # Skip files that includes sys headers for mingw.
         if [[ "$cc" = *"mingw"* ]]; then
            if [[ ${require_sys[$input]+_} ]]; then
               continue
            fi
         fi

         echo "$cc ${cflags[$cc]} --std=$std -c $input -o /dev/null" \
            >> $commands
      done
   done
done

# Generate commands for each C++ compiler+standard combination.
for cc in ${!cppflags[@]}; do
   if ! ( $cc --version > /dev/null 2>&1 ); then
      continue
   fi
   found_compilers=1

   for input in $file_pattern; do
      if [[ ! -s $input ]]; then
         continue
      fi

      # Add commands for each standard plus GNU extensions.
      for std in {c++,gnu++}{98,11,14,17,20}; do
         # Skip files that includes sys headers for mingw.
         if [[ "$cc" = *"mingw"* ]]; then
            if [[ ${require_sys[$input]+_} ]]; then
               continue
            fi
         fi

         echo "$cc ${cppflags[$cc]} --std=$std -c $input -o /dev/null" \
            >> $commands
      done
   done
done

# Run commands.
if [[ -s $commands ]]; then
   xargs -a $commands -d '\n' -P $cpu_count -n 1 bash -c
else
   if [[ $found_compilers -eq 0 ]]; then
      echo "Did not find any usable compilers"
   else
      echo "No files matched"
   fi
   rm $commands
   exit 1
fi

# Cleanup.
rm $commands
exit 0