Debugging information in GCC preprocessor output

Question

I was inspecting the preprocessed output generated by GCC, and I see a lot of these in the .i file that I generated using the -save-temps flag:

Answer 1

Based on the documentation the number before the filename is the line number. The numbers after the file name are a flag and mean the following:

• 1 indicates the start of a new file.
• 2 indicates returning to a file (after having included another file).
• 3 indicates that the following text comes from a system header file, so certain warnings should be suppressed.
• 4 indicates that the following text should be treated as being wrapped in an implicit extern "C" block.