cmake: Fix the build on Unix with source files checked out on Windows

The issue is that, by default, Git for Windows checks out text files
with CRLF line endings. This is a problem for awk, which is expecting
Unix-style LF line endings. When cloning on Windows and attempting to
compile on WSL, Mingw or Cygwin, there may be an error from awk.

The fix is to leverage CMake's ability to configure a file and perform
EOL conversions. We copy the awk scripts from the source directory to
the build directory. This portable method ensures they have LF endings,
and the build logic is updated to use the build directory version.

Intentionally avoiding .gitattributes to avoid setting precedent.

Co-authored-by: Christopher Sean Morrison <brlcad@gmail.com>
Co-authored-by: Cosmin Truta <ctruta@gmail.com>
Signed-off-by: Cosmin Truta <ctruta@gmail.com>

2 files changed, 20 insertions, 4 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 3b7db9e73..941cacb49 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -18,6 +18,7 @@
 # Revised by Alex Gaynor, 2020
 # Revised by Owen Rudge, 2020
 # Revised by Gleb Mazovetskiy, 2021
+# Revised by Christopher Sean Morrison, 2022
 
 # This code is released under the libpng license.
 # For conditions of distribution and use, see the disclaimer
@@ -293,6 +294,20 @@ if(NOT AWK OR ANDROID OR IOS)
                  ${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.h)
   add_custom_target(genfiles) # Dummy
 else()
+  # Copy the awk scripts, converting their line endings to Unix (LF)
+  configure_file(${CMAKE_CURRENT_SOURCE_DIR}/scripts/checksym.awk
+                 ${CMAKE_CURRENT_BINARY_DIR}/scripts/checksym.awk
+                 @ONLY
+                 NEWLINE_STYLE LF)
+  configure_file(${CMAKE_CURRENT_SOURCE_DIR}/scripts/options.awk
+                 ${CMAKE_CURRENT_BINARY_DIR}/scripts/options.awk
+                 @ONLY
+                 NEWLINE_STYLE LF)
+  configure_file(${CMAKE_CURRENT_SOURCE_DIR}/scripts/dfn.awk
+                 ${CMAKE_CURRENT_BINARY_DIR}/scripts/dfn.awk
+                 @ONLY
+                 NEWLINE_STYLE LF)
+
   # Generate .chk from .out with awk:
   # generate_chk(INPUT inputfile OUTPUT outputfile [DEPENDS dep1 [dep2...]])
   include(CMakeParseArguments)
@@ -377,14 +392,14 @@ else()
   # Generate scripts/pnglibconf.h
   generate_source(OUTPUT "scripts/pnglibconf.c"
                   DEPENDS "${CMAKE_CURRENT_SOURCE_DIR}/scripts/pnglibconf.dfa"
-                          "${CMAKE_CURRENT_SOURCE_DIR}/scripts/options.awk"
+                          "${CMAKE_CURRENT_BINARY_DIR}/scripts/options.awk"
                           "${CMAKE_CURRENT_SOURCE_DIR}/pngconf.h")
   add_custom_target(scripts_pnglibconf_c DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf.c")
 
   # Generate pnglibconf.c
   generate_source(OUTPUT "pnglibconf.c"
                   DEPENDS "${CMAKE_CURRENT_SOURCE_DIR}/scripts/pnglibconf.dfa"
-                          "${CMAKE_CURRENT_SOURCE_DIR}/scripts/options.awk"
+                          "${CMAKE_CURRENT_BINARY_DIR}/scripts/options.awk"
                           "${CMAKE_CURRENT_SOURCE_DIR}/pngconf.h")
   add_custom_target(pnglibconf_c DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.c")
 
@@ -446,7 +461,7 @@ else()
   generate_chk(INPUT "${CMAKE_CURRENT_BINARY_DIR}/scripts/symbols.out"
                OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/scripts/symbols.chk"
                DEPENDS scripts_symbols_out
-                       "${CMAKE_CURRENT_SOURCE_DIR}/scripts/checksym.awk"
+                       "${CMAKE_CURRENT_BINARY_DIR}/scripts/checksym.awk"
                        "${CMAKE_CURRENT_SOURCE_DIR}/scripts/symbols.def")
 
   add_custom_target(scripts_symbols_chk
diff --git a/scripts/genchk.cmake.in b/scripts/genchk.cmake.in
index ab3b9d746..1b6aa84ae 100644
--- a/scripts/genchk.cmake.in
+++ b/scripts/genchk.cmake.in
@@ -10,6 +10,7 @@
 
 # Variables substituted from CMakeLists.txt
 set(SRCDIR "@CMAKE_CURRENT_SOURCE_DIR@")
+set(BINDIR "@CMAKE_CURRENT_BINARY_DIR@")
 
 set(AWK "@AWK@")
 
@@ -23,7 +24,7 @@ get_filename_component(OUTPUTDIR "${OUTPUT}" PATH)
 if("${INPUTEXT}" STREQUAL ".out" AND "${OUTPUTEXT}" STREQUAL ".chk")
   # Generate .chk from .out with awk (generic)
   file(REMOVE "${OUTPUT}" "${OUTPUTDIR}/${OUTPUTBASE}.new")
-  execute_process(COMMAND "${AWK}" -f "${SRCDIR}/scripts/checksym.awk"
+  execute_process(COMMAND "${AWK}" -f "${BINDIR}/scripts/checksym.awk"
                           "${SRCDIR}/scripts/${INPUTBASE}.def"
                           "of=${OUTPUTDIR}/${OUTPUTBASE}.new"
                           "${INPUT}"