3 files changed, 61 insertions, 27 deletions
diff --git a/src/nvim/README.md b/src/nvim/README.md
index 660e3d1010..1c1c3c364e 100644
--- a/src/nvim/README.md
+++ b/src/nvim/README.md
@@ -1,13 +1,20 @@
+Nvim core source
+================
 
-Module-specific details are documented at the top of each module (e.g.
-terminal.c, screen.c).
+Module-specific details are documented at the top of each module (`terminal.c`,
+`screen.c`, ...).
 
-See also `:help development`.
+See `:help development` for more guidelines.
 
-UI Debugging
-------------
+Logs
+----
 
-At `DEBUG_LOG_LEVEL`, all UI events are logged.
+Low-level log messages sink to `$NVIM_LOG_FILE`.
+
+You can use `LOG_CALLSTACK()` anywhere in the source to log the current
+stacktrace. (Currently Linux-only.)
+
+UI events are logged at level 0 (`DEBUG_LOG_LEVEL`).
 
     rm -rf build/
     make CMAKE_EXTRA_FLAGS="-DMIN_LOG_LEVEL=0"
diff --git a/src/nvim/log.c b/src/nvim/log.c
index f1dbe61dda..252fe5438d 100644
--- a/src/nvim/log.c
+++ b/src/nvim/log.c
@@ -173,6 +173,53 @@ FILE *open_log_file(void)
   return stderr;
 }
 
+#if defined(__linux__)
+# include <execinfo.h>
+void log_callstack(const char *const func_name, const int line_num)
+{
+  void *trace[100];
+  int trace_size = backtrace(trace, ARRAY_SIZE(trace));
+
+  char exepath[MAXPATHL] = { 0 };
+  size_t exepathlen = MAXPATHL;
+  if (os_exepath(exepath, &exepathlen) != 0) {
+    abort();
+  }
+  assert(24 + exepathlen < IOSIZE);  // Must fit in `cmdbuf` below.
+
+  do_log(DEBUG_LOG_LEVEL, func_name, line_num, true, "trace:");
+
+  char cmdbuf[IOSIZE + (20 * ARRAY_SIZE(trace))];
+  snprintf(cmdbuf, sizeof(cmdbuf), "addr2line -e %s -f -p", exepath);
+  for (int i = 1; i < trace_size; i++) {
+    char buf[20];  // 64-bit pointer 0xNNNNNNNNNNNNNNNN with leading space.
+    snprintf(buf, sizeof(buf), " %p", trace[i]);
+    xstrlcat(cmdbuf, buf, sizeof(cmdbuf));
+  }
+  // Now we have a command string like:
+  //    addr2line -e /path/to/exe -f -p 0x123 0x456 ...
+
+  log_lock();
+  FILE *log_file = open_log_file();
+  if (log_file == NULL) {
+    goto end;
+  }
+
+  FILE *fp = popen(cmdbuf, "r");
+  char linebuf[IOSIZE];
+  while (fgets(linebuf, sizeof(linebuf) - 1, fp) != NULL) {
+    fprintf(log_file, "  %s", linebuf);
+  }
+  pclose(fp);
+
+  if (log_file != stderr && log_file != stdout) {
+    fclose(log_file);
+  }
+end:
+  log_unlock();
+}
+#endif
+
 static bool do_log_to_file(FILE *log_file, int log_level,
                            const char *func_name, int line_num, bool eol,
                            const char* fmt, ...)
diff --git a/src/nvim/log.h b/src/nvim/log.h
index 48be7606e7..2bd18f5776 100644
--- a/src/nvim/log.h
+++ b/src/nvim/log.h
@@ -62,27 +62,7 @@
 #endif
 
 #if defined(__linux__)
-# include <execinfo.h>
-# define LOG_CALLSTACK(prefix) \
-  do { \
-    void *trace[100]; \
-    int trace_size = backtrace(trace, 100); \
-    \
-    char exe[1024]; \
-    ssize_t elen = readlink("/proc/self/exe", exe, sizeof(exe) - 1); \
-    exe[elen] = 0; \
-    \
-    for (int i = 1; i < trace_size; i++) { \
-      char buf[256]; \
-      snprintf(buf, sizeof(buf), "addr2line -e %s -f -p %p", exe, trace[i]); \
-      FILE *fp = popen(buf, "r"); \
-      while (fgets(buf, sizeof(buf) - 1, fp) != NULL) { \
-        buf[strlen(buf)-1] = 0; \
-        do_log(DEBUG_LOG_LEVEL, __func__, __LINE__, true, prefix "%s", buf); \
-      } \
-      fclose(fp); \
-    } \
-  } while (0)
+# define LOG_CALLSTACK() log_callstack(__func__, __LINE__)
 #endif
 
 #ifdef INCLUDE_GENERATED_DECLARATIONS