Avoid calling back() on an empty string in setBinaryenBinDir (#5280)

std::string::back() is only well defined for non-empty strings.
Without the change, wasm-reduce fails if it is called from
$PATH, because then, the parent directory is an empty string.
A workaround is to explicitly set the binaryen path with -b,
and it is still necessary after this fix, but at least the program
ends with a comprehensible error message instead of a generic
assertion failure from the standard library.

1 files changed, 1 insertions, 1 deletions

diff --git a/src/support/path.cpp b/src/support/path.cpp
index d3f5075c2..1858fe1e9 100644
--- a/src/support/path.cpp
+++ b/src/support/path.cpp
@@ -81,7 +81,7 @@ std::string getBinaryenBinDir() {
 
 void setBinaryenBinDir(const std::string& dir) {
   binDir = dir;
-  if (binDir.back() != getPathSeparator()) {
+  if (binDir.empty() || binDir.back() != getPathSeparator()) {
     binDir += getPathSeparator();
   }
 }