链接外部库时出现 Rcpp 错误？

Question

我正在用头撞墙，试图让

Rcpp

在 Raspberry Pi 上构建 SPI 包。

我的代码/包可以在我的 GitHub 上找到：https://github.com/mnr/rpigpior/

当我跑步

Rcpp::compileAttributes()

，然后是

load_all()

时，我一直得到

RcppExports.cpp：14：32：错误：'spi_config_t'尚未声明

很明显我还没有声明或链接一些重要的东西 - 但我不清楚我需要在哪里声明链接以及我需要链接什么。

有人有过这样的经历吗？

从位于 https://github.com/mnr/rpigpior/

的包源开始

> Rcpp::compileAttributes()
> load_all()

ℹ Loading rpigpior
Exports from /home/pi/Documents/rpigpior/src/rpi_spi_open.cpp:
   int rpi_spi_open(char *device, spi_config_t config)

/home/pi/Documents/rpigpior/src/RcppExports.cpp updated.
/home/pi/Documents/rpigpior/R/RcppExports.R updated.
ℹ Re-compiling rpigpior (debug build)
── R CMD INSTALL ───────────────────────────────────────────────────────────────────────────────────────────────────
─  installing *source* package ‘rpigpior’ ... (730ms)
   ** using staged installation
   ** libs
   using C compiler: ‘gcc (Raspbian 10.2.1-6+rpi1) 10.2.1 20210110’
   using C++ compiler: ‘g++ (Raspbian 10.2.1-6+rpi1) 10.2.1 20210110’
   g++ -std=gnu++17 -I"/opt/R/release/lib/R/include" -DNDEBUG  -I'/home/pi/R/armv7l-unknown-linux-gnueabihf-library/4.3/Rcpp/include' -I/usr/local/include    -fPIC  -g -O2  -UNDEBUG -Wall -pedantic -g -O0 -fdiagnostics-color=always -c RcppExports.cpp -o RcppExports.o
   RcppExports.cpp:14:32: error: ‘spi_config_t’ has not been declared
      14 | int rpi_spi_open(char *device, spi_config_t config);
         |                                ^~~~~~~~~~~~
   RcppExports.cpp: In function ‘SEXPREC* _rpigpior_rpi_spi_open(SEXPREC**, SEXP)’:
   RcppExports.cpp:19:57: error: cannot convert ‘SEXP’ {aka ‘SEXPREC*’} to ‘Rcpp::traits::input_parameter<char>::type*’ {aka ‘Rcpp::InputParameter<char>*’} in initialization
      19 |     Rcpp::traits::input_parameter< char >::type *device(*deviceSEXP);
         |                                                         ^~~~~~~~~~~
         |                                                         |
         |                                                         SEXP {aka SEXPREC*}
   In file included from /home/pi/R/armv7l-unknown-linux-gnueabihf-library/4.3/Rcpp/include/Rcpp/r/headers.h:67,
                    from /home/pi/R/armv7l-unknown-linux-gnueabihf-library/4.3/Rcpp/include/RcppCommon.h:30,
                    from /home/pi/R/armv7l-unknown-linux-gnueabihf-library/4.3/Rcpp/include/Rcpp.h:27,
                    from RcppExports.cpp:4:
   /opt/R/release/lib/R/include/Rinternals.h:180:16: note: class type ‘SEXPREC’ is incomplete
     180 | typedef struct SEXPREC *SEXP;
         |                ^~~~~~~
   RcppExports.cpp:20:36: error: ‘spi_config_t’ was not declared in this scope
      20 |     Rcpp::traits::input_parameter< spi_config_t >::type config(configSEXP);
         |                                    ^~~~~~~~~~~~
   RcppExports.cpp:20:49: error: template argument 1 is invalid
      20 |     Rcpp::traits::input_parameter< spi_config_t >::type config(configSEXP);
         |                                                 ^
   RcppExports.cpp:20:57: error: expected initializer before ‘config’
      20 |     Rcpp::traits::input_parameter< spi_config_t >::type config(configSEXP);
         |                                                         ^~~~~~
   RcppExports.cpp:21:56: error: ‘config’ was not declared in this scope
      21 |     rcpp_result_gen = Rcpp::wrap(rpi_spi_open(*device, config));
         |                                                        ^~~~~~
   make: *** [/opt/R/release/lib/R/etc/Makeconf:200: RcppExports.o] Error 1
   ERROR: compilation failed for package ‘rpigpior’
─  removing ‘/tmp/RtmpN8Haun/devtools_install_10981336a33c/rpigpior’
Error in `(function (command = NULL, args = character(), error_on_status = TRUE, …`:
! System command 'R' failed
---
Exit status: 1
stdout & stderr: <printed>
---

Answer 1

查看错误信息：

   RcppExports.cpp:14:32: error: ‘spi_config_t’ has not been declared
      14 | int rpi_spi_open(char *device, spi_config_t config);
         |                                ^~~~~~~~~~~~
   RcppExports.cpp: In function ‘SEXPREC* _rpigpior_rpi_spi_open(SEXPREC**, SEXP)’:
   RcppExports.cpp:19:57: error: cannot convert ‘SEXP’ {aka ‘SEXPREC*’} to ‘Rcpp::traits::input_parameter<char>::type*’ {aka ‘Rcpp::InputParameter<char>*’} in initialization
      19 |     Rcpp::traits::input_parameter< char >::type *device(*deviceSEXP);

我们看到入口点或粘合函数没有使用标准 Rcpp 数据类型和/或为自定义结构定义转换器。

// [[Rcpp::export]]
int rpi_spi_open(char *device, spi_config_t config) {

https://github.com/mnr/rpigpior/blob/8aac7aa71eaadbb599d5ab615b005d4b9886c4a3/src/rpi_spi_open.cpp#L20C18-L20C30

在这种情况下，尝试为

as

结构定义必要的

wrap()

/

spi_config_t

函数，或者直接在 C++ 函数内部初始化它，并允许参数包含支持的类型。

您可以在此处查看创建自定义

wrap()

/

as()

的有效示例：

https://gallery.rcpp.org/articles/custom-templated-wrap-and-as-for-seamingless-interfaces/