__cxa_throw(): Print exception info

edolstra · cole-h · commit f69b305e6066 · 2026-03-31T07:16:06.000-07:00
Example:

  Aborting on unexpected exception of type 'St16invalid_argument', error: bitset::_M_copy_from_ptr
diff --git a/nix-meson-build-support/common/cxa-throw/interpose-cxa-throw.cc b/nix-meson-build-support/common/cxa-throw/interpose-cxa-throw.cc
@@ -4,16 +4,12 @@
 
 #include "is-logic-error.hh"
 
-#ifndef CXA_THROW_ON_LOGIC_ERROR
-#  define CXA_THROW_ON_LOGIC_ERROR() abort()
-#endif
-
 typedef void (*cxa_throw_type)(void *, std::type_info *, void (*)(void *));
 
 extern "C" void __cxa_throw(void * exc, std::type_info * tinfo, void (*dest)(void *))
 {
     if (is_logic_error(tinfo))
-        CXA_THROW_ON_LOGIC_ERROR();
+        abort_on_exception(exc, tinfo);
 
     static auto * orig = (cxa_throw_type) dlsym(RTLD_NEXT, "__cxa_throw");
     if (!orig)
diff --git a/nix-meson-build-support/common/cxa-throw/is-logic-error.hh b/nix-meson-build-support/common/cxa-throw/is-logic-error.hh
@@ -1,8 +1,14 @@
 #pragma once
 
+#include <unistd.h>
 #include <cxxabi.h>
 #include <stdexcept>
 #include <typeinfo>
+#include <cstring>
+
+#ifndef CXA_THROW_ON_LOGIC_ERROR
+#  define CXA_THROW_ON_LOGIC_ERROR() abort()
+#endif
 
 static bool is_logic_error(const std::type_info * tinfo)
 {
@@ -15,3 +21,20 @@ static bool is_logic_error(const std::type_info * tinfo)
 
     return false;
 }
+
+static void abort_on_exception(void * exc, const std::type_info * tinfo)
+{
+    if (!is_logic_error(tinfo))
+        return;
+
+    char buf[512];
+    snprintf(
+        buf,
+        sizeof(buf),
+        "Aborting on unexpected exception of type '%s', error: %s\n",
+        tinfo->name(),
+        ((std::exception *) exc)->what());
+    [[maybe_unused]] auto r = write(STDERR_FILENO, buf, strlen(buf));
+
+    CXA_THROW_ON_LOGIC_ERROR();
+}
diff --git a/nix-meson-build-support/common/cxa-throw/wrap-cxa-throw.cc b/nix-meson-build-support/common/cxa-throw/wrap-cxa-throw.cc
@@ -3,16 +3,12 @@
 
 #include "is-logic-error.hh"
 
-#ifndef CXA_THROW_ON_LOGIC_ERROR
-#  define CXA_THROW_ON_LOGIC_ERROR() abort()
-#endif
-
 extern "C" void __real___cxa_throw(void *, std::type_info *, void (*)(void *));
 
 extern "C" void __wrap___cxa_throw(void * exc, std::type_info * tinfo, void (*dest)(void *))
 {
     if (is_logic_error(tinfo))
-        CXA_THROW_ON_LOGIC_ERROR();
+        abort_on_exception(exc, tinfo);
 
     __real___cxa_throw(exc, tinfo, dest);
 
