From 70a9abfaff37aa2bcdcaee92230bf2a096d14261 Mon Sep 17 00:00:00 2001
From: Peter Barker <pbarker@barker.dropbear.id.au>
Date: Thu, 30 Apr 2020 15:09:40 +1000
Subject: [PATCH] AP_InternalError: emit stringification of internal errors

---
 libraries/AP_Arming/AP_Arming.cpp             |  2 +-
 .../AP_InternalError/AP_InternalError.cpp     | 56 +++++++++++++++++++
 libraries/AP_InternalError/AP_InternalError.h | 11 ++++
 3 files changed, 68 insertions(+), 1 deletion(-)

diff --git a/libraries/AP_Arming/AP_Arming.cpp b/libraries/AP_Arming/AP_Arming.cpp
index 96d86c9ff4..1d64b1f45d 100644
--- a/libraries/AP_Arming/AP_Arming.cpp
+++ b/libraries/AP_Arming/AP_Arming.cpp
@@ -783,7 +783,7 @@ bool AP_Arming::system_checks(bool report)
     if (AP::internalerror().errors() != 0) {
         uint8_t buffer[32];
         AP::internalerror().errors_as_string(buffer, ARRAY_SIZE(buffer));
-        check_failed(report, "Internal errors 0x%x l:%u (%s)", (unsigned int)AP::internalerror().errors(), AP::internalerror().last_error_line(), buffer);
+        check_failed(report, "Internal errors 0x%x l:%u %s", (unsigned int)AP::internalerror().errors(), AP::internalerror().last_error_line(), buffer);
         return false;
     }
 
diff --git a/libraries/AP_InternalError/AP_InternalError.cpp b/libraries/AP_InternalError/AP_InternalError.cpp
index 3579b90c61..28d11f248c 100644
--- a/libraries/AP_InternalError/AP_InternalError.cpp
+++ b/libraries/AP_InternalError/AP_InternalError.cpp
@@ -27,6 +27,62 @@ void AP_InternalError::error(const AP_InternalError::error_t e, uint16_t line) {
     hal.util->persistent_data.internal_error_last_line = line;
 }
 
+void AP_InternalError::errors_as_string(uint8_t *buffer, const uint16_t len) const
+{
+    static const char * const error_bit_descriptions[] {
+        "mapfailure",  // logger_mapfailure
+        "miss_struct",  // logger_missing_logstructure
+        "write_mssfmt",  // logger_logwrite_missingfmt
+        "many_deletes",  // logger_too_many_deletions
+        "bad_getfile",  // logger_bad_getfilename
+        "unused1",
+        "flush_no_sem",  // logger_flushing_without_sem
+        "bad_curr_blk",  // logger_bad_current_block
+        "blkcnt_bad",  // logger_blockcount_mismatch
+        "dq_failure",  // logger_dequeue_failure
+        "cnstring_nan",  // constraining_nan
+        "watchdog_rst",  // watchdog_reset
+        "iomcu_reset",
+        "iomcu_fail",
+        "spi_fail",
+        "main_loop_stk",  // main_loop_stuck
+        "gcs_bad_link",  // gcs_bad_missionprotocol_link
+        "bitmask_range",
+        "gcs_offset",
+        "i2c_isr",
+        "flow_of_ctrl",  // flow_of_control
+        "sfs_recursion",  // switch_full_sector_recursion
+        "bad_rotation",
+        "stack_ovrflw",  // stack_overflow
+    };
+
+    static_assert((1U<<(ARRAY_SIZE(error_bit_descriptions))) == uint32_t(AP_InternalError::error_t::__LAST__), "too few descriptions for bits");
+
+    buffer[0] = 0;
+    uint32_t buffer_used = 0;
+    for (uint8_t i=0; i<ARRAY_SIZE(error_bit_descriptions); i++) {
+        if (buffer_used >= len) {
+            break;
+        }
+        if (internal_errors & (1U<<i)) {
+            const char *format;
+            if (i == 0) {
+                format = "%s";
+            } else {
+                format = ",%s";
+            }
+            const size_t written = hal.util->snprintf((char*)&buffer[buffer_used],
+                                                      len-buffer_used,
+                                                      format,
+                                                      error_bit_descriptions[i]);
+            if (written <= 0) {
+                break;
+            }
+            buffer_used += written;
+        }
+    }
+}
+
 namespace AP {
 
 AP_InternalError &internalerror()
diff --git a/libraries/AP_InternalError/AP_InternalError.h b/libraries/AP_InternalError/AP_InternalError.h
index 257fbfa092..266100ca45 100644
--- a/libraries/AP_InternalError/AP_InternalError.h
+++ b/libraries/AP_InternalError/AP_InternalError.h
@@ -57,11 +57,22 @@ public:
         switch_full_sector_recursion= (1U << 21),  //0x200000  2097152
         bad_rotation                = (1U << 22),  //0x400000  4194304
         stack_overflow              = (1U << 23),  //0x800000  8388608
+        __LAST__                    = (1U << 24),  // used only for sanity check
     };
 
+    // if you've changed __LAST__ to be 32, then you will want to
+    // rejig the way we do sanity checks as we don't want to move to a
+    // 64-bit type for error_t:
+    static_assert(sizeof(error_t) == 4, "error_t should be 32-bit type");
+
     uint16_t last_error_line() const { return last_line; }
 
     void error(const AP_InternalError::error_t error, uint16_t line);
+
+    // fill buffer with a description of the exceptions present in
+    // internal errors.  buffer will always be null-terminated.
+    void errors_as_string(uint8_t *buffer, uint16_t len) const;
+
     uint32_t count() const { return total_error_count; }
 
     // internal_errors - return mask of internal errors seen