fixed portability issue with gcc10's default linker behavior (new def…

…ault is -fno-common, so had to add extern keyword to some headerfile declarations); added CRAN-check instructions for adding that flag to the devtools::check()

README.md

@@ -15,10 +15,22 @@ install_github("opsani/soobench")
 
 If you make changes, before you submit a PR, please help me out by running
 ```
-./do check package
+./do check
 ```
 to ensure the changes will be accepted by the CRAN team.
 
+### Portability concerns
+To check using the `gcc10 -fno-common` [requirement](https://cran.r-project.org/doc/manuals/r-release/R-exts.html#Portable-C-and-C_002b_002b-code),
+use
+```
+withr::with_makevars(
+  c(
+    "CFLAGS"="-Wall -pedantic -fdiagnostics-color=always -fno-common"
+  ),
+  devtools::check()
+)
+```
+
 [![CRAN Status Badge](http://www.r-pkg.org/badges/version/soobench)](http://cran.r-project.org/web/packages/soobench)
 [![CRAN Downloads](http://cranlogs.r-pkg.org/badges/soobench)](http://cran.rstudio.com/web/packages/soobench/index.html)
 

src/benchmarksnoisy.h

@@ -33,5 +33,5 @@ TwoDoubles f130(double *x);
 void initbenchmarksnoisy();
 void finibenchmarksnoisy();
 
-bbobFunction handlesNoisy[30];
-unsigned int handlesNoisyLength;
+extern bbobFunction handlesNoisy[30];
+extern unsigned int handlesNoisyLength;