The following issue has been SUBMITTED.
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https://cmake.org/Bug/view.php?id=16077
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Reported By: skebanga
Assigned To:
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Project: CMake
Issue ID: 16077
Category: Modules
Reproducibility: always
Severity: minor
Priority: normal
Status: new
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Date Submitted: 2016-04-22 17:09 EDT
Last Modified: 2016-04-22 17:09 EDT
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Summary: FindProtobuf.cmake doesn't have required flexibility
to configure protoc usage for all use cases
Description:
I have here a very simple test project which has 2 protobuf files, one of which
is included in the other.
Using cmake, I will create a static library for each generated protobuf message.
##Protobuf files:
**`src/foo/message.proto`:**
package test.foo;
message FooMsg
{
required string s = 1;
}
**`src/bar/message.proto`:**
package test.bar;
import "foo/message.proto";
message BarMsg
{
optional foo.FooMsg f = 1;
}
##CMake files:
I build `lib_foo` from generated `foo/message.proto` files.
**`src/foo/CMakeLists.txt`:**
protobuf_generate_cpp(PROTO_SRCS PROTO_HDRS message.proto)
add_library(lib_foo STATIC ${PROTO_SRCS})
I build `lib_bar` from the generated `bar/message.proto` files, and link in
`lib_foo`:
**`src/bar/CMakeLists.txt`:**
protobuf_generate_cpp(PROTO_SRCS PROTO_HDRS message.proto )
add_library(lib_bar STATIC ${PROTO_SRCS})
target_link_libraries(lib_bar lib_foo)
**`src/CMakeLists.txt`:**
cmake_minimum_required (VERSION 3.5)
project (cmake_proto_test CXX)
find_package(Protobuf REQUIRED)
# proto files import from the source root directory, so add the required -I
flag
set(PROTOBUF_IMPORT_DIRS ${CMAKE_SOURCE_DIR})
# genererated proto files go into the CMake binary output dir
include_directories("${CMAKE_BINARY_DIR}")
add_subdirectory(foo)
add_subdirectory(bar)
##Build error:
When I try to build this, I get the following error:
$ make .. VERBOSE=1
cd src/cmake_proto/build/bar && /usr/bin/c++
-I src/cmake_proto/build
-o CMakeFiles/lib_bar.dir/message.pb.cc.o
-c src/cmake_proto/build/bar/message.pb.cc
In file included from src/cmake_proto/build/bar/message.pb.cc:5:0:
src/cmake_proto/build/bar/message.pb.h:99:24:
error: ‘foo’ in namespace ‘test’ does not name a type
inline const ::test::foo::FooMsg& f() const;
^
##Reason:
The error is due to the header guard created by `protoc` being the same for the
2 generated files:
#ifndef PROTOBUF_message_2eproto__INCLUDED
#define PROTOBUF_message_2eproto__INCLUDED
...
#endif
The reason is that the header guard is derived from a combination of the output
directory and the generated file's path.
The current command issued by `FindProtobuf.cmake` results in the header guard
only using the filename:
cd src/cmake_proto/build/foo && /usr/local/bin/protoc --cpp_out
src/cmake_proto/build/foo -I src/cmake_proto/foo -I src/cmake_proto
src/cmake_proto/foo/message.proto
cd src/cmake_proto/build/bar && /usr/local/bin/protoc --cpp_out
src/cmake_proto/build/bar -I src/cmake_proto/bar -I src/cmake_proto
src/cmake_proto/bar/message.proto
This command, however, will result in the files being generated in the same
location, but with a different header guard:
cd src/cmake_proto/build && /usr/local/bin/protoc --cpp_out
src/cmake_proto/build -I src/cmake_proto src/cmake_proto/foo/message.proto
cd src/cmake_proto/build && /usr/local/bin/protoc --cpp_out
src/cmake_proto/build -I src/cmake_proto src/cmake_proto/bar/message.proto
Header guards:
PROTOBUF_foo_2fmessage_2eproto__INCLUDED
PROTOBUF_bar_2fmessage_2eproto__INCLUDED
There are three key differences here:
- The `WORKING_DIRECTORY` from which `protoc` is run from is
`${CMAKE_BINARY_DIR}`
- The `--cpp_out` directory passed to `protoc` is `${CMAKE_BINARY_DIR}`
- The `-I` include path passed to `protoc` does **not** include the folder where
the proto file is found
Being able to control these 3 items would give the flexibility required to use
this tool in the above setup.
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Issue History
Date Modified Username Field Change
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2016-04-22 17:09 skebanga New Issue
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