Directly inject c++ code using presets

[agibsonccc]

Hi Sam: Is there a way to inject c++ code using presets?

I tried doing something like this:

  .put(new Info("#define INLINE_CVG_PROFILE_FUNC_ENTER \"none\"").cppText("\n" +
                        "static FILE *fp_trace = fopen(\"trace2.out\", \"a\");\n" +
                        "static int current_stack_depth = -1;\n" +
                        "static bool last_frame_was_resolved = false;\n" +
                        "\n" +
                        "__attribute__ ((constructor))\n" +
                        "NO_INSTRUMENT\n" +
                        "void trace_begin() {\n" +
                        "    fp_trace = fopen(\"trace.out\", \"a\");\n" +
                        "}\n" +
                        "\n" +
                        "__attribute__ ((destructor))\n" +
                        "NO_INSTRUMENT\n" +
                        "void trace_end() {\n" +
                        "    if(fp_trace != nullptr) {\n" +
                        "        fclose(fp_trace);\n" +
                        "    }\n" +
                        "}\n" +
                        "\n" +
                        "extern \"C\" NO_INSTRUMENT\n" +
                        "void __cyg_profile_func_enter(void *callee, void *caller) {\n" +
                        "printf(\"Calling fp enter\\n\",0);\n" +
                        "if(fp_trace != nullptr) {\n" +
                        "        last_frame_was_resolved = false;\n" +
                        "        auto maybe_resolved = instrumentation::resolve(callee, caller);\n" +
                        "        if (!maybe_resolved) { return; }\n" +
                        "        last_frame_was_resolved = true;\n" +
                        "        current_stack_depth++;\n" +
                        "        fprintf(fp_trace, \"%s\\n\", utils::format(*maybe_resolved, current_stack_depth).c_str());\n" +
                        "    }\n" +
                        "}\n" +
                        "\n" +
                        "extern \"C\" NO_INSTRUMENT\n" +
                        "void __cyg_profile_func_exit (void *callee, void *caller) {\n" +
                        "printf(\"Calling fp exit\\n\",0);\n" +
                        "\n" +
                        "    if(fp_trace != nullptr && last_frame_was_resolved) {\n" +
                        "        current_stack_depth--;\n" +
                        "        //fprintf(fp_trace, \"x %p %p %lu\\n\", callee, caller, time(nullptr));\n" +
                        "    }\n" +
                        "}\n").define(true))

The use case is fairly simple. -finstrument-functions causes the compiler to generate enter and exit calls using these method signatures.
The issue is (after using LD_DEBUG) that it loads the symbols from libc (which is a no op). The best way I've seen to handle this case is to use -Bsymbolic-functions or something similar to force the loader to prioritize locally defined symbols.

Ideally I can inject the code in to the generated jni cpp and then the loader will load it from there.

[saudet]

We can put stuff like that in a separate file like this: https://github.com/bytedeco/javacpp-presets/blob/master/opencv/src/main/resources/org/bytedeco/opencv/include/opencv_adapters.h
And include it with @Platform(include=...

[agibsonccc]

@saudet thanks for getting back to me. Are you saying that the include= will embed the desired code as part of the binary? I was hoping the function I specified would show up in the actual c++ file that's generated.

[saudet]

That's technically what the include directive does, we don't need to have something to copy/paste it there.

[agibsonccc]

Thanks. My mistake was thinking it was only applicable during the parse step. I was only familiar with the part of the lifecycle where you parse the file and add pre processors and other signals for it to generate method signature not also inlining code. (javacpp files are pretty big after all!)