nimforum mirror - Tracking down SIGSEGV. What's the difference between this Nim and C code?

giaco (orginal) [2022-01-13T02:51:28+01:00] view original

I've been scratching my head solving a SIGSEGV on my machine when using futhark. I've reduced the problem to a self contained Nim and C files with no external nim packages involved, just plain C linkage.

The C program compiles and runs correctly, the Nim program goes SIGSEGV while calling C function, but they should be almost 1:1, can you help me track down the problem?

The program should link with -lclang. I've reproduced the problem on libclang-10, libclang-11, libclang-12, both gclib and musl, so the problem must be somewhere on the nim side.

You can find dockerfiles for reproducible builds and Makefile here: https://github.com/arkanoid87/futhest

futhest.c

#include "clang-c/Index.h"

int main (void) {
    CXIndex Idx = clang_createIndex(0, 0);
    
    const int args = 2;
    const char *commandLineArgs[args];
    commandLineArgs[0] = "-I/usr/lib/clang/10/include";
    commandLineArgs[1] = "-I/usr/include";
    
    CXTranslationUnit TU = clang_parseTranslationUnit(Idx,
        "futhark-includes.h", commandLineArgs, args, 0, 0, 0);
    
    CXCursor cursor = clang_getTranslationUnitCursor(TU);
    
    clang_disposeTranslationUnit(TU);
}

futhest.nim

type
  CXIndex = pointer
  CXTranslationUnit = pointer
  CXCursor = pointer


#[
CINDEX_LINKAGE CXIndex clang_createIndex(int excludeDeclarationsFromPCH,
                                         int displayDiagnostics);
]#
proc createIndex*(excludeDeclarationsFromPCH: cint; displayDiagnostics: cint): CXIndex {.
    importc: "clang_createIndex", cdecl.}


#[
CINDEX_LINKAGE CXTranslationUnit
clang_parseTranslationUnit(CXIndex CIdx,
                           const char *source_filename,
                           const char *const *command_line_args,
                           int num_command_line_args,
                           struct CXUnsavedFile *unsaved_files,
                           unsigned num_unsaved_files,
                           unsigned options);
]#
proc parseTranslationUnit*(CIdx: CXIndex; source_filename: cstring;
                          command_line_args: cstringArray;
                          num_command_line_args: cint;
                          unsaved_files: pointer;
                          num_unsaved_files: cuint; options: cuint): CXTranslationUnit {.
    importc: "clang_parseTranslationUnit", cdecl.}


#[
  CINDEX_LINKAGE CXCursor clang_getTranslationUnitCursor(CXTranslationUnit);
]#
proc getTranslationUnitCursor*(a1: CXTranslationUnit): CXCursor {.
    importc: "clang_getTranslationUnitCursor", cdecl.}


#[
  CINDEX_LINKAGE void clang_disposeTranslationUnit(CXTranslationUnit);
]#
proc disposeTranslationUnit*(a1: CXTranslationUnit) {.importc: "clang_disposeTranslationUnit", cdecl.}


# ----------------------------------------------------------------------------


static:
  # any content will fail, including empty file
  writeFile("futhark-includes.h", """
  #include "ldap.h"
""")

var
  commandLineParams = @[
    "-I/usr/lib/clang/10/include",
    "-I/usr/include"]
  index = createIndex(0, 0)
  commandLineArgs = allocCStringArray(commandLineParams)


var unit = parseTranslationUnit(index,
  "futhark-includes.h".cstring,
  commandLineArgs, commandLineParams.len.cint, nil, 0, 0)
deallocCStringArray(commandLineArgs)

var cursor = getTranslationUnitCursor(unit) # SIGSEGV

disposeTranslationUnit(unit)

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8796 :: Tracking down SIGSEGV. What's the difference between this Nim and C code?