Add support for modules loaded at runtime

README.md

@@ -39,6 +39,7 @@ Cpptrace also has a C API, docs [here](docs/c-api.md).
   - [Headers](#headers)
   - [Libdwarf Tuning](#libdwarf-tuning)
   - [JIT Support](#jit-support)
+  - [Loading Libraries at Runtime](#loading-libraries-at-runtime)
 - [Supported Debug Formats](#supported-debug-formats)
 - [How to Include The Library](#how-to-include-the-library)
   - [CMake FetchContent](#cmake-fetchcontent)
@@ -939,6 +940,12 @@ registered with cpptrace.
 
 [jitci]: https://sourceware.org/gdb/current/onlinedocs/gdb.html/JIT-Interface.html
 
+## Loading Libraries at Runtime
+
+When loading libraries at runtime, e.g. with `dlopen` or `LoadLibrary`, 
+`cpptrace::experimental::load_symbols_from_file` should be called with the path to the library. 
+Otherwise, `cpptrace` will not be able to resolve symbols in the library.
+
 # Supported Debug Formats
 
 | Format                       | Supported |

include/cpptrace/utils.hpp

@@ -49,6 +49,10 @@ namespace cpptrace {
         CPPTRACE_EXPORT void set_dwarf_resolver_line_table_cache_size(nullable<std::size_t> max_entries);
         CPPTRACE_EXPORT void set_dwarf_resolver_disable_aranges(bool disable);
     }
+
+    namespace experimental {
+        CPPTRACE_EXPORT void load_symbols_for_file(const std::string& filename);
+    }
 }
 
 #endif

src/symbols/symbols_with_dbghelp.cpp

@@ -1,6 +1,7 @@
 #ifdef CPPTRACE_GET_SYMBOLS_WITH_DBGHELP
 
 #include <cpptrace/basic.hpp>
+#include <cpptrace/utils.hpp>
 #include "symbols/symbols.hpp"
 #include "platform/dbghelp_utils.hpp"
 #include "binary/object.hpp"
@@ -18,6 +19,7 @@
 #endif
 #include <windows.h>
 #include <dbghelp.h>
+#include <psapi.h>
 
 namespace cpptrace {
 namespace detail {
@@ -449,4 +451,76 @@ namespace dbghelp {
 }
 }
 
+namespace cpptrace {
+namespace experimental {
+/*
+When a module was loaded at runtime with LoadLibrary after SymInitialize was already called,
+it is necessary to manually load the symbols from that module with SymLoadModuleEx.
+
+See "Symbol Handler Initialization" in Microsoft documentation at
+https://learn.microsoft.com/en-us/windows/win32/debug/symbol-handler-initialization
+*/
+void load_symbols_for_file(const std::string& name) {
+    HMODULE module = GetModuleHandleA(name.c_str());
+    if (module == NULL) {
+        std::fprintf(
+            stderr, 
+            "Error: Unable to load symbols for file %s: %s\n", 
+            name.c_str(), 
+            std::system_error(GetLastError(), std::system_category()).what()
+        );
+        return;
+    }
+
+    MODULEINFO moduleInfo;
+    if (0 == GetModuleInformation(
+        GetCurrentProcess(),
+        module,
+        &moduleInfo,
+        sizeof(moduleInfo)
+    )) {
+        std::fprintf(
+            stderr, 
+            "Error: Unable to get module information for %s: %s\n", 
+            name.c_str(), 
+            std::system_error(GetLastError(), std::system_category()).what()
+        );
+        return;
+    }
+
+    auto lock = cpptrace::detail::get_dbghelp_lock();
+    HANDLE syminit_handle = cpptrace::detail::ensure_syminit().get_process_handle();
+    if (0 == SymLoadModuleEx(
+        syminit_handle,
+        NULL,
+        name.c_str(),
+        NULL,
+        (DWORD64)moduleInfo.lpBaseOfDll,
+        moduleInfo.SizeOfImage,
+        NULL,
+        0
+    )) {
+        std::fprintf(
+            stderr, 
+            "Error: Unable to load symbols for file %s: %s\n", 
+            name.c_str(), 
+            std::system_error(GetLastError(), std::system_category()).what()
+        );
+    }
+}
+}
+}
+#else
+
+#include <cpptrace/utils.hpp>
+
+namespace cpptrace {
+namespace experimental {
+
+void load_symbols_for_file(const std::string& name) {
+    (void)name;
+}
+}
+
+}
 #endif