libpngconf.c is attached to multiple targets

[mgood7123]

CMake Error in /Users/smallville7123/StudioProjects/Graphical-Tool-Kit/app/src/main/cpp/freetype-cmake/libpng/CMakeLists.txt:
The custom command generating

/Users/smallville7123/StudioProjects/Graphical-Tool-Kit/macOS/IMPORTED_CMAKE_PROJECTS/OpenGLApp_CMAKE_PROJECT/GRAPHICS/libpng/pnglibconf.c

is attached to multiple targets:

genfiles
gensym
genvers

but none of these is a common dependency of the other(s). This is not
allowed by the Xcode "new build system".

when generating cmake project for XCode

[mgood7123]

this seems to be fixed with the following

--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -263,11 +263,17 @@ if(UNIX)
   symbol_prefix()
 endif()
 
-find_program(AWK NAMES gawk awk)
+if(CMAKE_GENERATOR MATCHES "Xcode" AND CMAKE_XCODE_BUILD_SYSTEM MATCHES 12)
+  message(WARNING "libpng does not currently support generating files for multiple targets using the Xcode \"new build system\", libpng will use the prebuilt pnglibconf instead")
+  set(PNG_XCODE_NEW_BUILD_SYSTEM true)
+else()
+  set(PNG_XCODE_NEW_BUILD_SYSTEM false)
+  find_program(AWK NAMES gawk awk)
+endif()
 
 include_directories(${CMAKE_CURRENT_BINARY_DIR})
 
-if(NOT AWK OR ANDROID OR IOS)
+if (PNG_XCODE_NEW_BUILD_SYSTEM OR NOT AWK OR ANDROID OR IOS)
   # No awk available to generate sources; use pre-built pnglibconf.h
   configure_file(${CMAKE_CURRENT_SOURCE_DIR}/scripts/pnglibconf.h.prebuilt
                  ${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.h)
@@ -449,7 +455,7 @@ else()
                             "${CMAKE_CURRENT_BINARY_DIR}/scripts/symbols.chk"
                             "${CMAKE_CURRENT_BINARY_DIR}/scripts/symbols.out"
                             "${CMAKE_CURRENT_BINARY_DIR}/scripts/vers.out")
-endif(NOT AWK OR ANDROID OR IOS)
+endif(PNG_XCODE_NEW_BUILD_SYSTEM OR NOT AWK OR ANDROID OR IOS)
 
 # List the source code files.
 set(libpng_public_hdrs
@@ -463,8 +469,10 @@ set(libpng_private_hdrs
     pnginfo.h
     pngstruct.h
 )
-if(AWK AND NOT ANDROID AND NOT IOS)
+if(NOT PNG_XCODE_NEW_BUILD_SYSTEM AND AWK AND NOT ANDROID AND NOT IOS)
  list(APPEND libpng_private_hdrs "${CMAKE_CURRENT_BINARY_DIR}/pngprefix.h")
 endif()
 set(libpng_sources
     ${libpng_public_hdrs}

[glebm]

There is a clean fix in #403

[code-affinity]

I am facing the same error while building libpng 1.6.37 (because that is the version that is currently snapshotted in the latest version of the ImageMagick source distribution) with Xcode 12.4. Although #403 was applied to 1.6.38, I locally applied the changes from #403 to CMakeLists.txt for version 1.6.37, but I still get "attached to multiple targets" errors, although now it identifies different problem targets than before:

[08:31:15] : [Step 2/5] CMake Error in CMakeLists.txt:
[08:31:15] : [Step 2/5] The custom command generating
[08:31:15] : [Step 2/5]
[08:31:15] : [Step 2/5] /Users/build/buildAgent/work/64fba3137de0b35f/third-party/build/libpng-prefix/src/libpng-build/scripts/sym.out
[08:31:15] : [Step 2/5]
[08:31:15] : [Step 2/5] is attached to multiple targets:
[08:31:15] : [Step 2/5]
[08:31:15] : [Step 2/5] gensym
[08:31:15] : [Step 2/5] genfiles
[08:31:15] : [Step 2/5]
[08:31:15] : [Step 2/5] but none of these is a common dependency of the other(s). This is not
[08:31:15] : [Step 2/5] allowed by the Xcode "new build system".

I do not claim to understand what "none of these is a common dependency of the other(s)" means.

The custom command that generates sym.out is:

  generate_out(INPUT "${CMAKE_CURRENT_SOURCE_DIR}/scripts/sym.c"
               OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/scripts/sym.out"
               DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.h" pnglibconf_h)
  add_custom_target(scripts_sym_out DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/scripts/sym.out")

The rules for the gensym target are:

  generate_copy(INPUT "${CMAKE_CURRENT_BINARY_DIR}/scripts/sym.out"
                OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/libpng.sym"
                DEPENDS scripts_sym_out)
  add_custom_target(gensym DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/libpng.sym")

The genfiles target depends on both the scripts_sym_out target and the gensym target:

  add_custom_target(genfiles
                    DEPENDS "${CMAKE_CURRENT_BINARY_DIR}/libpng.sym" gensym
                            "${CMAKE_CURRENT_BINARY_DIR}/libpng.vers" genvers
                            "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.c" pnglibconf_c
                            "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.h" pnglibconf_h
                            "${CMAKE_CURRENT_BINARY_DIR}/pnglibconf.out" pnglibconf_out
                            "${CMAKE_CURRENT_BINARY_DIR}/pngprefix.h" pngprefix_h
                            "${CMAKE_CURRENT_BINARY_DIR}/scripts/intprefix.out" scripts_intprefix_out
                            "${CMAKE_CURRENT_BINARY_DIR}/scripts/pnglibconf.c" scripts_pnglibconf_c
                            "${CMAKE_CURRENT_BINARY_DIR}/scripts/prefix.out" scripts_prefix_out
                            "${CMAKE_CURRENT_BINARY_DIR}/scripts/sym.out" scripts_sym_out
                            "${CMAKE_CURRENT_BINARY_DIR}/scripts/symbols.chk" symbol-check
                            "${CMAKE_CURRENT_BINARY_DIR}/scripts/symbols.out" scripts_symbols_out
                            "${CMAKE_CURRENT_BINARY_DIR}/scripts/vers.out" scripts_vers_out)

I believe this is exactly the state of affairs that results from #403, but it is not working in the context of the 1.6.37 CMakeLists.txt.

[glebm]

v1.6.37 is older than the current libpng16 branch. If my fix is merged, the issue will be fixed in the next 1.6 release

[code-affinity]

I understand. However, I have to work with what is available to me now, so I took matters into my own hands by applying the same changes to the older version. The 1.6.37 and 1.6.38 CMakeLists.txt are similar enough that the #403 changes were pretty straightforward to apply.

[code-affinity]

The more expedient solution in my case was to invoke CMake with "-T buildsystem=1", which tells it to use the old XCode build system that can tolerate the libpng CMakeLists.txt design.

[ctruta]

Fixed.