Address short comings with printf for strings

src/printf.cpp

@@ -165,14 +165,20 @@ void process_printf(char*& data, const printf_descriptor_map_t& descs,
 
     std::stringstream printf_out{};
 
-    // Firstly print the part of the format string up to the first '%'
+    // Firstly print the part of the format string up to the first '%' if any
+    // otherwise print the whole string as is and move the data pointer to the
+    // end.
     size_t next_part = format_string.find_first_of('%');
-    printf_out << format_string.substr(0, next_part);
-
+    if (next_part == std::string::npos) {
+        printf_out << format_string;
+        data = data_end;
+    } else {
+        printf_out << format_string.substr(0, next_part);
+    }
     // Decompose the remaining format string into individual strings with
     // one format specifier each, handle each one individually
     size_t arg_idx = 0;
-    while (next_part < format_string.size() - 1) {
+    while (next_part < format_string.size()) {
         // Get the part of the format string before the next format specifier
         size_t part_start = next_part;
         size_t part_end = format_string.find_first_of('%', part_start + 1);
@@ -181,7 +187,17 @@ void process_printf(char*& data, const printf_descriptor_map_t& descs,
         // Handle special cases
         if (part_end == part_start + 1) {
             printf_out << "%";
-            next_part = part_end + 1;
+            size_t next_format = format_string.find_first_of('%', part_end + 1);
+            // Check if there is anything to print between two %
+            if (next_format != std::string::npos &&
+                next_format - part_end > 1) {
+                // Print everything in between the two %
+                printf_out << format_string.substr(
+                    part_end + 1, next_format - (part_end + 1));
+                next_part = next_format;
+            } else {
+                next_part = part_end + 1;
+            }
             continue;
         } else if (part_end == std::string::npos &&
                    arg_idx >= descs.at(printf_id).arg_sizes.size()) {
@@ -210,8 +226,11 @@ void process_printf(char*& data, const printf_descriptor_map_t& descs,
             // Special case for %s
             if (get_fmt_conversion(part_fmt) == 's') {
                 uint32_t string_id = read_buff<uint32_t>(data);
-                printf_out << print_part(
-                    part_fmt, descs.at(string_id).format_string.c_str(), size);
+                if (string_id < descs.size()) {
+                    printf_out << print_part(
+                        part_fmt, descs.at(string_id).format_string.c_str(),
+                        size);
+                }
             } else {
                 printf_out << print_part(part_fmt, data, size);
             }

tests/api/printf.cpp

@@ -32,6 +32,18 @@ TEST_F(WithCommandQueueAndPrintf, SimplePrintf) {
     ASSERT_STREQ(m_printf_output.c_str(), message);
 }
 
+TEST_F(WithCommandQueueAndPrintf, SimpleFormatedPrintf) {
+    const char* source = "kernel void test_printf() { printf(\"%s\", \"\"); }";
+    auto kernel = CreateKernel(source, "test_printf");
+
+    size_t gws = 1;
+    size_t lws = 1;
+    EnqueueNDRangeKernel(kernel, 1, nullptr, &gws, &lws, 0, nullptr, nullptr);
+    Finish();
+
+    ASSERT_STREQ(m_printf_output.c_str(), "");
+}
+
 TEST_F(WithCommandQueueAndPrintf, TooLongPrintf) {
     // each print takes 12 bytes (4 for the printf_id, and 2*4 for the 2 integer
     // to print) + 4 for the byte written counter