Let's say I add the following to A.cpp

#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-parameter"
<code with unused parameters here>
#pragma GCC diagnostic pop

Then I build with "make -j." If "A.cpp" and "some_other_file_with_no_pragma.cpp" get built in parallel, will the #pragma above apply to both files? I would think not, but can't find a definitive answer.

CodePudding user response：

Not unless you are doing some really weird stuff in your Makefile.

Compiler compiles each translation unit(.cpp included .hpp) independently, meaning each pragma only applies to this one translation unit.

Running make -jN will execute N rules in parallel, each (line) in a separate shell process. Resulting in up to N parallel compilers which will not interfere with each other.

CodePudding user response：

… will the #pragma above apply to both files?

No. From the documentation (bold emphasis mine):

Note that these pragmas override any command-line options. GCC keeps track of the location of each pragma, and issues diagnostics according to the state as of that point in the source file. Thus, pragmas occurring after a line do not affect diagnostics caused by that line.