Edit GCC download_prerequisites for macOS

Since sometime during the development of GCC 7, GCC's download_prerequisites
script verifies the integrity of downloaded prerequisite tar balls using
"sha512sum" by default.  On macOS, this should be "shasum -a 512".  This
commit adjusts the OpenCoarrays edit_GCC_download_prereqs_file_if_necessary.sh
script so it can edit the download_prerequisites script to make the
file verification work on macOS.

Author: Damian Rouson

install.sh

@@ -161,6 +161,7 @@ info  "-l (--list-packages):    ${arg_l}"
 info  "-m (--with-cmake):       ${arg_m}"
 info  "-M (--with-mpi):         ${arg_M}"
 info  "-n (--no-color):         ${arg_n}"
+info  "-o (--only-download):    ${arg_o}"
 info  "-p (--package):          ${arg_p}"
 info  "-P (--print-path):       ${arg_P}"
 info  "-U (--print-url):        ${arg_U}"

prerequisites/build-functions/edit_GCC_download_prereqs_file_if_necessary.sh

@@ -1,26 +1,38 @@
-# Make the build directory, configure, and build
+
 # shellcheck disable=SC2154
 
 edit_GCC_download_prereqs_file_if_necessary()
 {
-  # Only modify download_prerequisites if wget is unavailable
-   if type wget &> /dev/null; then
-     info "wget available. Invoking unmodified GCC script contrib/download_prerequisites."
-   else 
-    info "wget unavailable. Editing GCC contrib/download_prerequisites to replace it with ${gcc_prereqs_fetch}"
+  __operating_system=$(uname)
+  download_prereqs_file="${PWD}/contrib/download_prerequisites"
 
-    download_prereqs_file="${PWD}/contrib/download_prerequisites"
-  
-    # Define a file extension for the download_prerequisites backup
-    backup_extension=".original"
-    backup_file="${download_prereqs_file}${backup_extension}"
-    if [[ -f ${backup_file}  ]]; then
-      # Prevent overwriting an existing backup:
-      backup_extension=""
-    fi
+  # Grab the line with the first occurence of 'wget'
+  wget_line=`grep wget "${download_prereqs_file}" | head -1` || true
+
+  # Check for wget format used before GCC 7
+  if [[ "${wget_line}" == *"ftp"* ]]; then
+    gcc7_format="false"
+    wget_command="${wget_line%%ftp*}" # grab everything before ftp
+
+  # Check for wget format adopted in GCC 7
+  elif [[  "${wget_line}" == *"base_url"* ]]; then 
+    gcc7_format="true"
+  fi
+
+  # Define a file extension for the download_prerequisites backup
+  backup_extension=".original"
+  backup_file="${download_prereqs_file}${backup_extension}"
+  if [[ -f ${backup_file}  ]]; then
+    # Prevent overwriting an existing backup:
+    backup_extension=""
+  fi
+
+  # Modify download_prerequisites if wget is unavailable
+  if type wget &> /dev/null; then
+    info "wget available. Leavingh wget invocations unmodified in the GCC script contrib/download_prerequisites."
+  else 
+    info "wget unavailable. Editing GCC contrib/download_prerequisites to replace it with ${gcc_prereqs_fetch}"
 
-    # Grab the line with the first occurence of 'wget'
-    wget_line=`grep wget "${download_prereqs_file}" | head -1` || true
     if [[ ! -z "${wget_line:-}"  ]]; then
       # Download_prerequisites contains wget so we haven't modified it
       already_modified_downloader="false"
@@ -36,14 +48,8 @@ edit_GCC_download_prereqs_file_if_necessary()
     # Only modify download_prerequisites once
     if [[ ${already_modified_downloader} != "true"  ]]; then
 
-      # Check for wget format used before GCC 7
-      if [[ "${wget_line}" == *"ftp"* ]]; then
-        gcc7_format="false"
-        wget_command="${wget_line%%ftp*}" # grab everything before ftp
+      if [[  "${gcc7_format}" == "true" ]]; then 
 
-      # Check for wget format adopted in GCC 7
-      elif [[  "${wget_line}" == *"base_url"* ]]; then 
-        gcc7_format="true"
         case "${gcc_prereqs_fetch}" in
           "ftp_url")
             # Insert a new line after line 2 to include ftp_url.sh as a download option
@@ -74,25 +80,44 @@ edit_GCC_download_prereqs_file_if_necessary()
             debug "if problem downloading, ensure that the gcc download_prerequisites edits are compatible with ${gcc_prereqs_fetch}"  
           ;;
         esac
-        # Protect against missing sha512sum command adopted in GCC 7 (not available by default on Lubuntu Linux)
-        if ! type sha512sum &> /dev/null; then
-          info "sha512sum unavailable. Turning off file integrity verification in GCC contrib/download_prerequisites."
-          if [[ "$(uname)" == "Linux" ]]; then
-            # Adjust for non-POSIX OS
-            sed -i"${backup_extension}" s/"verify=1"/"verify=0"/ "${download_prereqs_file}"
-          else
-            sed -i "${backup_extension}" s/"verify=1"/"verify=0"/ "${download_prereqs_file}"
-          fi
-        fi
       fi
-      info "Using the following command to replacing wget in the GCC download_prerequisites file:"
+      info "Using the following command to replace wget in the GCC download_prerequisites file:"
       info "sed -i${backup_extension} s/\"${wget_command}\"/\"${gcc_prereqs_fetch} ${arg_string} \"/ \"${download_prereqs_file}\""
-      if [[ "$(uname)" == "Linux" ]]; then
+      if [[ "${__operating_system}" == "Linux" ]]; then
         sed -i"${backup_extension}" s/"${wget_command}"/"${gcc_prereqs_fetch} ${arg_string} "/ "${download_prereqs_file}"
       else
         sed -i "${backup_extension}" s/"${wget_command}"/"${gcc_prereqs_fetch} ${arg_string} "/ "${download_prereqs_file}"
       fi
 
     fi # end if [[ ${already_modified_downloader:-} != "true"  ]];
-   fi # end if ! type wget &> /dev/null; 
+  fi # end if ! type wget &> /dev/null; 
+
+  if [[ "${gcc7_format:-}" == "true" ]]; then
+
+    # Protect against missing sha512sum command adopted in GCC 7 but unavailable on
+    # 1. Some Linux distributions (e.g., older Lubuntu distributions)
+    # 2. macOS, where the replacement is "shasum -a 512"
+
+    if ! type sha512sum &> /dev/null; then
+
+      info "sha512sum unavailable."
+      case "${__operating_system}" in
+        "Darwin" )
+          info "Substituting shasum -a 512"
+          sed -i "${backup_extension}" s/"\"\${chksum}sum\" --check"/"shasum -a 512 --check"/ "${download_prereqs_file}"
+         ;;
+        "Linux" )
+          info "Turning off file integrity verification in GCC contrib/download_prerequisites."
+          sed -i"${backup_extension}" s/"verify=1"/"verify=0"/ "${download_prereqs_file}"
+        ;;
+        *)
+          warning "Unrecognized operating system. Attempting to modify download_prerequisites with a 'sed' command synatax that assumes POSIX compliance."
+          info "Turning off file integrity verification in GCC contrib/download_prerequisites."
+          sed -i "${backup_extension}" s/"verify=1"/"verify=0"/ "${download_prereqs_file}"
+        ;;
+      esac
+
+    fi
+
+  fi
 }