libclang program to print the header files that are referenced by a call in a TU.

depgraph.c

/* clang depgraph.c -o depgraph -I tools/clang/include -lclang */
#include "clang-c/Index.h"
#include <stdio.h>

static enum CXChildVisitResult
visitor(CXCursor cursor, CXCursor parent, CXClientData client_data) {
  enum CXCursorKind kind = clang_getCursorKind(cursor);
  CXFile tu_file = (CXFile *)client_data;
  CXFile in_file, from_file;
  unsigned line, column, offset;
  CXSourceLocation loc;
  CXString tu_spelling, from_spelling;

  if (clang_isInvalid(kind))
    return CXChildVisit_Recurse;

  /* Just look for call expressions. */
  if (kind != CXCursor_CallExpr)
    return CXChildVisit_Recurse;

  /* Now check if the call is coming from the current file and calling into a
     different file (a header). */
  loc = clang_getCursorLocation(cursor);
  clang_getExpansionLocation(loc, &in_file, &line, &column, &offset);
  cursor = clang_getCursorReferenced(cursor);

  loc = clang_getCursorLocation(cursor);
  clang_getExpansionLocation(loc, &from_file, &line, &column, &offset);

  if (in_file != tu_file || from_file == tu_file)
    return CXChildVisit_Recurse;

  /* Print in graphviz format. */
  tu_spelling = clang_getFileName(tu_file);
  from_spelling = clang_getFileName(from_file);
  printf("\"%s\" -> \"%s\"\n", clang_getCString(tu_spelling),
         clang_getCString(from_spelling));
  clang_disposeString(tu_spelling);
  clang_disposeString(from_spelling);

  return CXChildVisit_Recurse;
}

int main(int argc, const char *argv[]) {
  CXIndex idx = clang_createIndex(1, 1);

  if (argc < 2)
    return 1;

  CXTranslationUnit tu = clang_createTranslationUnitFromSourceFile(
      idx, argv[1], argc - 2, argv + 2, 0, NULL);

  CXFile tu_file = clang_getFile(tu, argv[1]);
  clang_visitChildren(clang_getTranslationUnitCursor(tu), visitor, tu_file);

  clang_disposeTranslationUnit(tu);
  clang_disposeIndex(idx);
  return 0;
}