diff --git a/libqpdf/NNTree.cc b/libqpdf/NNTree.cc
index 170bf5c..85f2a94 100644
--- a/libqpdf/NNTree.cc
+++ b/libqpdf/NNTree.cc
@@ -9,6 +9,7 @@
 #include <qpdf/QPDF_private.hh>
 #include <qpdf/QTC.hh>
 #include <qpdf/QUtil.hh>
+#include <qpdf/Util.hh>
 
 #include <bit>
 #include <exception>
@@ -65,10 +66,8 @@ NNTreeIterator::updateIValue(bool allow_invalid)
     }
 
     if (item_number < 0 || !node) {
-        if (!allow_invalid) {
-            throw std::logic_error(
-                "attempt made to dereference an invalid name/number tree iterator");
-        }
+        util::assertion(
+            allow_invalid, "attempt made to dereference an invalid name/number tree iterator");
         return;
     }
     impl.error(node, "update ivalue: items array is too short");
@@ -210,9 +209,7 @@ NNTreeIterator::split(Dictionary to_split, std::list<PathElement>::iterator pare
     //   node: A
     //   item_number: 0
 
-    if (!valid()) {
-        throw std::logic_error("NNTreeIterator::split called an invalid iterator");
-    }
+    util::assertion(valid(), "NNTreeIterator::split called an invalid iterator");
 
     // Find the array we actually need to split, which is either this node's kids or items.
     Array kids = to_split["/Kids"];
@@ -228,13 +225,12 @@ NNTreeIterator::split(Dictionary to_split, std::list<PathElement>::iterator pare
         first_half = kids;
         n = nkids;
         key = "/Kids";
-    } else if (nitems > 0) {
+    } else {
+        util::assertion(nitems > 0, "NNTreeIterator::split called on invalid node");
         first_half = items;
         n = nitems;
         threshold *= 2;
         key = impl.itemsKey();
-    } else {
-        throw std::logic_error("NNTreeIterator::split called on invalid node");
     }
 
     if (n <= threshold) {
@@ -369,9 +365,7 @@ NNTreeIterator::remove()
 {
     // Remove this item, leaving the tree valid and this iterator pointing to the next item.
 
-    if (!valid()) {
-        throw std::logic_error("attempt made to remove an invalid iterator");
-    }
+    util::assertion(valid(), "attempt made to remove an invalid iterator");
     Array items = node[impl.itemsKey()];
     int nitems = static_cast<int>(items.size());
     if (std::cmp_greater(item_number + 2, nitems)) {
@@ -396,13 +390,12 @@ NNTreeIterator::remove()
             // the previous item.
             item_number -= 2;
             increment(false);
-        } else if (item_number < nitems) {
+        } else {
+            util::assertion(
+                item_number < nitems, "NNTreeIterator::remove: item_number > nitems after erase");
             // We don't have to do anything since the removed item's successor now occupies its
             // former location.
             updateIValue();
-        } else {
-            // We already checked to ensure this condition would not happen.
-            throw std::logic_error("NNTreeIterator::remove: item_number > nitems after erase");
         }
         return;
     }
diff --git a/libqpdf/Pl_AES_PDF.cc b/libqpdf/Pl_AES_PDF.cc
index 3d47b97..b5e0364 100644
--- a/libqpdf/Pl_AES_PDF.cc
+++ b/libqpdf/Pl_AES_PDF.cc
@@ -3,10 +3,13 @@
 #include <qpdf/QIntC.hh>
 #include <qpdf/QPDFCryptoProvider.hh>
 #include <qpdf/QUtil.hh>
+#include <qpdf/Util.hh>
+
 #include <cstring>
-#include <stdexcept>
 #include <string>
 
+using namespace qpdf;
+
 bool Pl_AES_PDF::use_static_iv = false;
 
 Pl_AES_PDF::Pl_AES_PDF(char const* identifier, Pipeline* next, bool encrypt, std::string key) :
@@ -15,12 +18,8 @@ Pl_AES_PDF::Pl_AES_PDF(char const* identifier, Pipeline* next, bool encrypt, std
     crypto(QPDFCryptoProvider::getImpl()),
     encrypt(encrypt)
 {
-    if (!next) {
-        throw std::logic_error("Attempt to create Pl_AES_PDF with nullptr as next");
-    }
-    if (!(key.size() == 32 || key.size() == 16)) {
-        throw std::runtime_error("unsupported key length");
-    }
+    util::assertion(next, "Attempt to create Pl_AES_PDF with nullptr as next");
+    util::no_ci_rt_error_if(!(key.size() == 32 || key.size() == 16), "unsupported key length");
     std::memset(this->inbuf, 0, this->buf_size);
     std::memset(this->outbuf, 0, this->buf_size);
     std::memset(this->cbc_block, 0, this->buf_size);
@@ -41,12 +40,10 @@ Pl_AES_PDF::disablePadding()
 void
 Pl_AES_PDF::setIV(unsigned char const* iv, size_t bytes)
 {
-    if (bytes != buf_size) {
-        throw std::logic_error(
-            "Pl_AES_PDF: specified initialization vector"
-            " size in bytes must be " +
+    util::assertion(
+        bytes == buf_size,
+        "Pl_AES_PDF: specified initialization vector size in bytes must be " +
             std::to_string(bytes));
-    }
     use_specified_iv = true;
     memcpy(specified_iv, iv, bytes);
 }
@@ -103,9 +100,7 @@ Pl_AES_PDF::finish()
             // This is never supposed to happen as the output is always supposed to be padded.
             // However, we have encountered files for which the output is not a multiple of the
             // block size.  In this case, pad with zeroes and hope for the best.
-            if (offset >= buf_size) {
-                throw std::logic_error("buffer overflow in AES encryption pipeline");
-            }
+            util::assertion(offset < buf_size, "buffer overflow in AES encryption pipeline");
             std::memset(inbuf + offset, 0, buf_size - offset);
             offset = buf_size;
         }
@@ -136,9 +131,7 @@ Pl_AES_PDF::initializeVector()
 void
 Pl_AES_PDF::flush(bool strip_padding)
 {
-    if (offset != buf_size) {
-        throw std::logic_error("AES pipeline: flush called when buffer was not full");
-    }
+    util::assertion(offset == buf_size, "AES pipeline: flush called when buffer was not full");
 
     if (first) {
         first = false;
diff --git a/libqpdf/Pl_ASCII85Decoder.cc b/libqpdf/Pl_ASCII85Decoder.cc
index 28905ec..0373d22 100644
--- a/libqpdf/Pl_ASCII85Decoder.cc
+++ b/libqpdf/Pl_ASCII85Decoder.cc
@@ -1,15 +1,17 @@
 #include <qpdf/Pl_ASCII85Decoder.hh>
 
 #include <qpdf/QTC.hh>
+#include <qpdf/Util.hh>
+
 #include <cstring>
 #include <stdexcept>
 
+using namespace qpdf;
+
 Pl_ASCII85Decoder::Pl_ASCII85Decoder(char const* identifier, Pipeline* next) :
     Pipeline(identifier, next)
 {
-    if (!next) {
-        throw std::logic_error("Attempt to create Pl_ASCII85Decoder with nullptr as next");
-    }
+    util::assertion(next, "Attempt to create Pl_ASCII85Decoder with nullptr as next");
 }
 
 void
@@ -33,12 +35,9 @@ Pl_ASCII85Decoder::write(unsigned char const* buf, size_t len)
         if (eod > 1) {
             break;
         } else if (eod == 1) {
-            if (buf[i] == '>') {
-                flush();
-                eod = 2;
-            } else {
-                throw std::runtime_error("broken end-of-data sequence in base 85 data");
-            }
+            util::no_ci_rt_error_if(buf[i] != '>', "broken end-of-data sequence in base 85 data");
+            flush();
+            eod = 2;
         } else {
             switch (buf[i]) {
             case '~':
@@ -48,12 +47,10 @@ Pl_ASCII85Decoder::write(unsigned char const* buf, size_t len)
             case 'z':
                 if (pos != 0) {
                     throw std::runtime_error("unexpected z during base 85 decode");
-                } else {
-                    QTC::TC("libtests", "Pl_ASCII85Decoder read z");
-                    unsigned char zeroes[4];
-                    memset(zeroes, '\0', 4);
-                    next()->write(zeroes, 4);
                 }
+                unsigned char zeroes[4];
+                memset(zeroes, '\0', 4);
+                next()->write(zeroes, 4);
                 break;
 
             default:
@@ -76,7 +73,6 @@ void
 Pl_ASCII85Decoder::flush()
 {
     if (this->pos == 0) {
-        QTC::TC("libtests", "Pl_ASCII85Decoder no-op flush");
         return;
     }
     unsigned long lval = 0;
diff --git a/libqpdf/Pl_ASCIIHexDecoder.cc b/libqpdf/Pl_ASCIIHexDecoder.cc
index 795dfc0..9df282e 100644
--- a/libqpdf/Pl_ASCIIHexDecoder.cc
+++ b/libqpdf/Pl_ASCIIHexDecoder.cc
@@ -1,17 +1,18 @@
 #include <qpdf/Pl_ASCIIHexDecoder.hh>
 
 #include <qpdf/QTC.hh>
+#include <qpdf/Util.hh>
+
 #include <cctype>
 #include <stdexcept>
 
+using namespace qpdf;
 using namespace std::literals;
 
 Pl_ASCIIHexDecoder::Pl_ASCIIHexDecoder(char const* identifier, Pipeline* next) :
     Pipeline(identifier, next)
 {
-    if (!next) {
-        throw std::logic_error("Attempt to create Pl_ASCIIHexDecoder with nullptr as next");
-    }
+    util::assertion(next, "Attempt to create Pl_ASCIIHexDecoder with nullptr as next");
 }
 
 void
diff --git a/libqpdf/Pl_Buffer.cc b/libqpdf/Pl_Buffer.cc
index 38fadb3..ef2b4a7 100644
--- a/libqpdf/Pl_Buffer.cc
+++ b/libqpdf/Pl_Buffer.cc
@@ -1,10 +1,14 @@
 #include <qpdf/Pl_Buffer.hh>
 
+#include <qpdf/Util.hh>
+
 #include <algorithm>
 #include <cstdlib>
 #include <cstring>
 #include <stdexcept>
 
+using namespace qpdf;
+
 class Pl_Buffer::Members
 {
   public:
@@ -50,9 +54,7 @@ Pl_Buffer::finish()
 Buffer*
 Pl_Buffer::getBuffer()
 {
-    if (!m->ready) {
-        throw std::logic_error("Pl_Buffer::getBuffer() called when not ready");
-    }
+    util::assertion(m->ready, "Pl_Buffer::getBuffer() called when not ready");
     auto* b = new Buffer(std::move(m->data));
     m->data.clear();
     return b;
@@ -61,9 +63,7 @@ Pl_Buffer::getBuffer()
 std::string
 Pl_Buffer::getString()
 {
-    if (!m->ready) {
-        throw std::logic_error("Pl_Buffer::getString() called when not ready");
-    }
+    util::assertion(m->ready, "Pl_Buffer::getString() called when not ready");
     auto s = std::move(m->data);
     m->data.clear();
     return s;
@@ -78,9 +78,7 @@ Pl_Buffer::getBufferSharedPointer()
 void
 Pl_Buffer::getMallocBuffer(unsigned char** buf, size_t* len)
 {
-    if (!m->ready) {
-        throw std::logic_error("Pl_Buffer::getMallocBuffer() called when not ready");
-    }
+    util::assertion(m->ready, "Pl_Buffer::getMallocBuffer() called when not ready");
     auto size = m->data.size();
     *len = size;
     if (size > 0) {
diff --git a/libqpdf/Pl_Concatenate.cc b/libqpdf/Pl_Concatenate.cc
index fa95bea..776f2eb 100644
--- a/libqpdf/Pl_Concatenate.cc
+++ b/libqpdf/Pl_Concatenate.cc
@@ -1,13 +1,13 @@
 #include <qpdf/Pl_Concatenate.hh>
 
-#include <stdexcept>
+#include <qpdf/Util.hh>
+
+using namespace qpdf;
 
 Pl_Concatenate::Pl_Concatenate(char const* identifier, Pipeline* next) :
     Pipeline(identifier, next)
 {
-    if (!next) {
-        throw std::logic_error("Attempt to create Pl_Concatenate with nullptr as next");
-    }
+    util::assertion(next, "Attempt to create Pl_Concatenate with nullptr as next");
 }
 
 // Must be explicit and not inline -- see QPDF_DLL_CLASS in README-maintainer
diff --git a/libqpdf/Pl_Count.cc b/libqpdf/Pl_Count.cc
index bca217c..2b9e261 100644
--- a/libqpdf/Pl_Count.cc
+++ b/libqpdf/Pl_Count.cc
@@ -1,6 +1,9 @@
 #include <qpdf/Pl_Count.hh>
 
 #include <qpdf/QIntC.hh>
+#include <qpdf/Util.hh>
+
+using namespace qpdf;
 
 class Pl_Count::Members
 {
@@ -18,15 +21,11 @@ Pl_Count::Pl_Count(char const* identifier, Pipeline* next) :
     Pipeline(identifier, next),
     m(std::make_unique<Members>())
 {
-    if (!next) {
-        throw std::logic_error("Attempt to create Pl_Count with nullptr as next");
-    }
+    util::assertion(next, "Attempt to create Pl_Count with nullptr as next");
 }
 
-Pl_Count::~Pl_Count() // NOLINT (modernize-use-equals-default)
-{
-    // Must be explicit and not inline -- see QPDF_DLL_CLASS in README-maintainer
-}
+Pl_Count::~Pl_Count() = default;
+// Must be explicit and not inline -- see QPDF_DLL_CLASS in README-maintainer
 
 void
 Pl_Count::write(unsigned char const* buf, size_t len)
diff --git a/libqpdf/Pl_DCT.cc b/libqpdf/Pl_DCT.cc
index 02abda1..b059d30 100644
--- a/libqpdf/Pl_DCT.cc
+++ b/libqpdf/Pl_DCT.cc
@@ -2,6 +2,7 @@
 
 #include <qpdf/QIntC.hh>
 #include <qpdf/QTC.hh>
+#include <qpdf/Util.hh>
 
 #include <csetjmp>
 #include <stdexcept>
@@ -11,6 +12,8 @@
 # error "qpdf does not support libjpeg built with BITS_IN_JSAMPLE != 8"
 #endif
 
+using namespace qpdf;
+
 namespace
 {
     class FunctionCallbackConfig: public Pl_DCT::CompressConfig
@@ -118,9 +121,7 @@ Pl_DCT::Pl_DCT(char const* identifier, Pipeline* next) :
     Pipeline(identifier, next),
     m(std::make_unique<Members>())
 {
-    if (!next) {
-        throw std::logic_error("Attempt to create Pl_DCT with nullptr as next");
-    }
+    util::assertion(next, "Attempt to create Pl_DCT with nullptr as next");
 }
 
 void
@@ -285,12 +286,10 @@ fill_buffer_input_buffer(j_decompress_ptr)
 static void
 skip_buffer_input_data(j_decompress_ptr cinfo, long num_bytes)
 {
-    if (num_bytes < 0) {
-        throw std::runtime_error(
-            "reading jpeg: jpeg library requested skipping a negative number of bytes");
-    }
+    util::no_ci_rt_error_if(
+        num_bytes < 0, "reading jpeg: jpeg library requested skipping a negative number of bytes");
     size_t to_skip = QIntC::to_size(num_bytes);
-    if ((to_skip > 0) && (to_skip <= cinfo->src->bytes_in_buffer)) {
+    if (to_skip > 0 && to_skip <= cinfo->src->bytes_in_buffer) {
         cinfo->src->next_input_byte += to_skip;
         cinfo->src->bytes_in_buffer -= to_skip;
     } else if (to_skip != 0) {
@@ -354,11 +353,10 @@ Pl_DCT::compress(void* cinfo_p)
     unsigned int width = cinfo->image_width * QIntC::to_uint(cinfo->input_components);
     size_t expected_size = QIntC::to_size(cinfo->image_height) *
         QIntC::to_size(cinfo->image_width) * QIntC::to_size(cinfo->input_components);
-    if (m->buf.size() != expected_size) {
-        throw std::runtime_error(
-            "Pl_DCT: image buffer size = " + std::to_string(m->buf.size()) +
+    util::no_ci_rt_error_if(
+        m->buf.size() != expected_size,
+        "Pl_DCT: image buffer size = " + std::to_string(m->buf.size()) +
             "; expected size = " + std::to_string(expected_size));
-    }
     JSAMPROW row_pointer[1];
     auto buffer = reinterpret_cast<unsigned char*>(m->buf.data());
     while (cinfo->next_scanline < cinfo->image_height) {
diff --git a/libqpdf/Pl_Flate.cc b/libqpdf/Pl_Flate.cc
index 9a575ad..63ff66d 100644
--- a/libqpdf/Pl_Flate.cc
+++ b/libqpdf/Pl_Flate.cc
@@ -6,12 +6,15 @@
 
 #include <qpdf/QIntC.hh>
 #include <qpdf/QUtil.hh>
+#include <qpdf/Util.hh>
 #include <qpdf/qpdf-config.h>
 
 #ifdef ZOPFLI
 # include <zopfli.h>
 #endif
 
+using namespace qpdf;
+
 namespace
 {
     unsigned long long memory_limit_{0};
@@ -31,10 +34,9 @@ Pl_Flate::Members::Members(size_t out_bufsize, action_e action) :
     // development files available, which particularly helps in a Windows environment.
     zdata = new z_stream;
 
-    if (out_bufsize > UINT_MAX) {
-        throw std::runtime_error(
-            "Pl_Flate: zlib doesn't support buffer sizes larger than unsigned int");
-    }
+    util::no_ci_rt_error_if(
+        out_bufsize > UINT_MAX,
+        "Pl_Flate: zlib doesn't support buffer sizes larger than unsigned int");
 
     z_stream& zstream = *(static_cast<z_stream*>(this->zdata));
     zstream.zalloc = nullptr;
@@ -70,9 +72,7 @@ Pl_Flate::Pl_Flate(
     Pipeline(identifier, next),
     m(std::make_unique<Members>(QIntC::to_size(out_bufsize_int), action))
 {
-    if (!next) {
-        throw std::logic_error("Attempt to create Pl_Flate with nullptr as next");
-    }
+    util::assertion(next, "Attempt to create Pl_Flate with nullptr as next");
 }
 
 // Must be explicit and not inline -- see QPDF_DLL_CLASS in README-maintainer
@@ -107,10 +107,8 @@ Pl_Flate::warn(char const* msg, int code)
 void
 Pl_Flate::write(unsigned char const* data, size_t len)
 {
-    if (!m->outbuf) {
-        throw std::logic_error(
-            this->identifier + ": Pl_Flate: write() called after finish() called");
-    }
+    util::assertion(
+        m->outbuf.get(), identifier + ": Pl_Flate: write() called after finish() called");
     if (m->zopfli_buf) {
         m->zopfli_buf->append(reinterpret_cast<char const*>(data), len);
         return;
@@ -131,9 +129,8 @@ Pl_Flate::write(unsigned char const* data, size_t len)
 void
 Pl_Flate::handleData(unsigned char const* data, size_t len, int flush)
 {
-    if (len > UINT_MAX) {
-        throw std::runtime_error("Pl_Flate: zlib doesn't support data blocks larger than int");
-    }
+    util::no_ci_rt_error_if(
+        len > UINT_MAX, "Pl_Flate: zlib doesn't support data blocks larger than int");
     z_stream& zstream = *(static_cast<z_stream*>(m->zdata));
     // zlib is known not to modify the data pointed to by next_in but doesn't declare the field
     // value const unless compiled to do so.
@@ -216,7 +213,6 @@ Pl_Flate::handleData(unsigned char const* data, size_t len, int flush)
 
         default:
             checkError("data", err);
-            break;
         }
     }
 }
diff --git a/libqpdf/Pl_LZWDecoder.cc b/libqpdf/Pl_LZWDecoder.cc
index cdb4d4d..71fb39c 100644
--- a/libqpdf/Pl_LZWDecoder.cc
+++ b/libqpdf/Pl_LZWDecoder.cc
@@ -2,17 +2,17 @@
 
 #include <qpdf/QIntC.hh>
 #include <qpdf/QTC.hh>
-#include <qpdf/QUtil.hh>
+#include <qpdf/Util.hh>
 #include <cstring>
 #include <stdexcept>
 
+using namespace qpdf;
+
 Pl_LZWDecoder::Pl_LZWDecoder(char const* identifier, Pipeline* next, bool early_code_change) :
     Pipeline(identifier, next),
     code_change_delta(early_code_change)
 {
-    if (!next) {
-        throw std::logic_error("Attempt to create Pl_LZWDecoder with nullptr as next");
-    }
+    util::assertion(next, "Attempt to create Pl_LZWDecoder with nullptr as next");
 }
 
 void
@@ -78,21 +78,17 @@ Pl_LZWDecoder::sendNextCode()
 unsigned char
 Pl_LZWDecoder::getFirstChar(unsigned int code)
 {
-    unsigned char result = '\0';
     if (code < 256) {
-        result = static_cast<unsigned char>(code);
-    } else if (code > 257) {
-        unsigned int idx = code - 258;
-        if (idx >= table.size()) {
-            throw std::runtime_error("Pl_LZWDecoder::getFirstChar: table overflow");
-        }
-        Buffer& b = table.at(idx);
-        result = b.getBuffer()[0];
-    } else {
-        throw std::runtime_error(
-            "Pl_LZWDecoder::getFirstChar called with invalid code (" + std::to_string(code) + ")");
+        return static_cast<unsigned char>(code);
     }
-    return result;
+    util::no_ci_rt_error_if(
+        code <= 257,
+        "Pl_LZWDecoder::getFirstChar called with invalid code (" + std::to_string(code) + ")");
+
+    unsigned int idx = code - 258;
+    util::no_ci_rt_error_if(idx >= table.size(), "Pl_LZWDecoder::getFirstChar: table overflow");
+    Buffer& b = table.at(idx);
+    return b.getBuffer()[0];
 }
 
 void
@@ -106,18 +102,16 @@ Pl_LZWDecoder::addToTable(unsigned char c)
         tmp[0] = static_cast<unsigned char>(last_code);
         last_data = tmp;
         last_size = 1;
-    } else if (last_code > 257) {
+    } else {
+        util::no_ci_rt_error_if(
+            last_code <= 257,
+            "Pl_LZWDecoder::addToTable called with invalid code (" + std::to_string(last_code) +
+                ")");
         unsigned int idx = last_code - 258;
-        if (idx >= table.size()) {
-            throw std::runtime_error("Pl_LZWDecoder::addToTable: table overflow");
-        }
+        util::no_ci_rt_error_if(idx >= table.size(), "Pl_LZWDecoder::addToTable: table overflow");
         Buffer& b = table.at(idx);
         last_data = b.getBuffer();
         last_size = QIntC::to_uint(b.getSize());
-    } else {
-        throw std::runtime_error(
-            "Pl_LZWDecoder::addToTable called with invalid code (" + std::to_string(last_code) +
-            ")");
     }
 
     Buffer entry(1 + last_size);
@@ -158,19 +152,16 @@ Pl_LZWDecoder::handleCode(unsigned int code)
                 } else if (idx == table_size) {
                     // The encoder would have just created this entry, so the first character of
                     // this entry would have been the same as the first character of the last entry.
-                    QTC::TC("libtests", "Pl_LZWDecoder last was table size");
                     next_c = getFirstChar(last_code);
                 } else {
                     next_c = getFirstChar(code);
                 }
             }
             unsigned int new_idx = 258 + table_size;
-            if (new_idx == 4096) {
-                throw std::runtime_error("LZWDecoder: table full");
-            }
+            util::no_ci_rt_error_if(new_idx == 4096, "LZWDecoder: table full");
             addToTable(next_c);
             unsigned int change_idx = new_idx + code_change_delta;
-            if ((change_idx == 511) || (change_idx == 1023) || (change_idx == 2047)) {
+            if (change_idx == 511 || change_idx == 1023 || change_idx == 2047) {
                 ++code_size;
             }
         }
diff --git a/libqpdf/Pl_RC4.cc b/libqpdf/Pl_RC4.cc
index a71ace1..78ea1be 100644
--- a/libqpdf/Pl_RC4.cc
+++ b/libqpdf/Pl_RC4.cc
@@ -1,24 +1,23 @@
 #include <qpdf/Pl_RC4.hh>
 
 #include <qpdf/QUtil.hh>
+#include <qpdf/Util.hh>
+
+using namespace qpdf;
 
 Pl_RC4::Pl_RC4(char const* identifier, Pipeline* next, std::string key, size_t out_bufsize) :
     Pipeline(identifier, next),
     out_bufsize(out_bufsize),
     rc4(reinterpret_cast<unsigned char const*>(key.data()), static_cast<int>(key.size()))
 {
-    if (!next) {
-        throw std::logic_error("Attempt to create Pl_RC4 with nullptr as next");
-    }
+    util::assertion(next, "Attempt to create Pl_RC4 with nullptr as next");
     this->outbuf = QUtil::make_shared_array<unsigned char>(out_bufsize);
 }
 
 void
 Pl_RC4::write(unsigned char const* data, size_t len)
 {
-    if (this->outbuf == nullptr) {
-        throw std::logic_error(this->identifier + ": Pl_RC4: write() called after finish() called");
-    }
+    util::assertion(outbuf.get(), "Pl_RC4: write() called after finish() called");
 
     size_t bytes_left = len;
     unsigned char const* p = data;
@@ -26,7 +25,6 @@ Pl_RC4::write(unsigned char const* data, size_t len)
     while (bytes_left > 0) {
         size_t bytes = (bytes_left < this->out_bufsize ? bytes_left : out_bufsize);
         bytes_left -= bytes;
-        // lgtm[cpp/weak-cryptographic-algorithm]
         rc4.process(p, bytes, outbuf.get());
         p += bytes;
         next()->write(outbuf.get(), bytes);
diff --git a/libqpdf/Pl_SHA2.cc b/libqpdf/Pl_SHA2.cc
index 546ff63..1b11317 100644
--- a/libqpdf/Pl_SHA2.cc
+++ b/libqpdf/Pl_SHA2.cc
@@ -2,8 +2,9 @@
 
 #include <qpdf/QPDFCryptoProvider.hh>
 #include <qpdf/QUtil.hh>
+#include <qpdf/Util.hh>
 
-#include <stdexcept>
+using namespace qpdf;
 
 Pl_SHA2::Pl_SHA2(int bits, Pipeline* next) :
     Pipeline("sha2", next)
@@ -49,9 +50,7 @@ Pl_SHA2::finish()
 void
 Pl_SHA2::resetBits(int bits)
 {
-    if (in_progress) {
-        throw std::logic_error("bit reset requested for in-progress SHA2 Pipeline");
-    }
+    util::assertion(!in_progress, "bit reset requested for in-progress SHA2 Pipeline");
     crypto = QPDFCryptoProvider::getImpl();
     crypto->SHA2_init(bits);
 }
@@ -59,17 +58,13 @@ Pl_SHA2::resetBits(int bits)
 std::string
 Pl_SHA2::getRawDigest()
 {
-    if (in_progress) {
-        throw std::logic_error("digest requested for in-progress SHA2 Pipeline");
-    }
+    util::assertion(!in_progress, "digest requested for in-progress SHA2 Pipeline");
     return crypto->SHA2_digest();
 }
 
 std::string
 Pl_SHA2::getHexDigest()
 {
-    if (in_progress) {
-        throw std::logic_error("digest requested for in-progress SHA2 Pipeline");
-    }
+    util::assertion(!in_progress, "digest requested for in-progress SHA2 Pipeline");
     return QUtil::hex_encode(getRawDigest());
 }
diff --git a/libqpdf/QPDF.cc b/libqpdf/QPDF.cc
index 3dabac0..d86f604 100644
--- a/libqpdf/QPDF.cc
+++ b/libqpdf/QPDF.cc
@@ -672,10 +672,7 @@ QPDF::getXRefTable()
 std::map<QPDFObjGen, QPDFXRefEntry> const&
 Objects::xref_table()
 {
-    if (!m->parsed) {
-        throw std::logic_error("QPDF::getXRefTable called before parsing.");
-    }
-
+    util::assertion(m->parsed, "QPDF::getXRefTable called before parsing");
     return m->xref_table;
 }
 
diff --git a/libqpdf/QPDFArgParser.cc b/libqpdf/QPDFArgParser.cc
index 18cb501..3ec6cad 100644
--- a/libqpdf/QPDFArgParser.cc
+++ b/libqpdf/QPDFArgParser.cc
@@ -56,7 +56,6 @@ QPDFArgParser::selectOptionTable(std::string const& name)
 {
     auto t = m->option_tables.find(name);
     if (t == m->option_tables.end()) {
-        QTC::TC("libtests", "QPDFArgParser select unregistered table");
         throw std::logic_error("QPDFArgParser: selecting unregistered option table " + name);
     }
     m->option_table = &(t->second);
@@ -67,7 +66,6 @@ void
 QPDFArgParser::registerOptionTable(std::string const& name, bare_arg_handler_t end_handler)
 {
     if (m->option_tables.contains(name)) {
-        QTC::TC("libtests", "QPDFArgParser register registered table");
         throw std::logic_error(
             "QPDFArgParser: registering already registered option table " + name);
     }
@@ -80,7 +78,6 @@ QPDFArgParser::OptionEntry&
 QPDFArgParser::registerArg(std::string const& arg)
 {
     if (m->option_table->contains(arg)) {
-        QTC::TC("libtests", "QPDFArgParser duplicate handler");
         throw std::logic_error(
             "QPDFArgParser: adding a duplicate handler for option " + arg + " in " +
             m->option_table_name + " option table");
@@ -138,7 +135,6 @@ QPDFArgParser::addInvalidChoiceHandler(std::string const& arg, param_arg_handler
 {
     auto i = m->option_table->find(arg);
     if (i == m->option_table->end()) {
-        QTC::TC("libtests", "QPDFArgParser invalid choice handler to unknown");
         throw std::logic_error(
             "QPDFArgParser: attempt to add invalid choice handler to unknown argument");
     }
@@ -448,11 +444,9 @@ QPDFArgParser::parseArgs()
             // Special case for -- option, which is used to break out of subparsers.
             oep = m->option_table->find("--");
             end_option = true;
-            if (oep == m->option_table->end()) {
-                // This is registered automatically, so this can't happen.
-                throw std::logic_error("QPDFArgParser: -- handler not registered");
-            }
-        } else if ((arg[0] == '-') && (strcmp(arg, "-") != 0)) {
+            util::internal_error_if(
+                oep == m->option_table->end(), "QPDFArgParser: -- handler not registered");
+        } else if (arg[0] == '-' && strcmp(arg, "-") != 0) {
             ++arg;
             if (arg[0] == '-') {
                 // Be lax about -arg vs --arg
@@ -678,15 +672,12 @@ QPDFArgParser::addHelpTopic(
     std::string const& topic, std::string const& short_text, std::string const& long_text)
 {
     if (topic == "all") {
-        QTC::TC("libtests", "QPDFArgParser add reserved help topic");
         throw std::logic_error("QPDFArgParser: can't register reserved help topic " + topic);
     }
     if (topic.empty() || topic.at(0) == '-') {
-        QTC::TC("libtests", "QPDFArgParser bad topic for help");
         throw std::logic_error("QPDFArgParser: help topics must not start with -");
     }
     if (m->help_topics.contains(topic)) {
-        QTC::TC("libtests", "QPDFArgParser add existing topic");
         throw std::logic_error("QPDFArgParser: topic " + topic + " has already been added");
     }
 
@@ -701,17 +692,14 @@ QPDFArgParser::addOptionHelp(
     std::string const& short_text,
     std::string const& long_text)
 {
-    if (!((option_name.length() > 2) && (option_name.at(0) == '-') && (option_name.at(1) == '-'))) {
-        QTC::TC("libtests", "QPDFArgParser bad option for help");
+    if (!(option_name.length() > 2 && option_name.starts_with("--"))) {
         throw std::logic_error("QPDFArgParser: options for help must start with --");
     }
     if (m->option_help.contains(option_name)) {
-        QTC::TC("libtests", "QPDFArgParser duplicate option help");
         throw std::logic_error("QPDFArgParser: option " + option_name + " already has help");
     }
     auto ht = m->help_topics.find(topic);
     if (ht == m->help_topics.end()) {
-        QTC::TC("libtests", "QPDFArgParser add to unknown topic");
         throw std::logic_error(
             "QPDFArgParser: unable to add option " + option_name + " to unknown help topic " +
             topic);
diff --git a/libqpdf/qpdf/Util.hh b/libqpdf/qpdf/Util.hh
index 9e3c499..fa2f419 100644
--- a/libqpdf/qpdf/Util.hh
+++ b/libqpdf/qpdf/Util.hh
@@ -35,6 +35,14 @@ namespace qpdf::util
         }
     }
 
+    inline void
+    no_ci_rt_error_if(bool cond, std::string const& msg)
+    {
+        if (cond) {
+            throw std::runtime_error(msg);
+        }
+    }
+
     inline constexpr char
     hex_decode_char(char digit)
     {
diff --git a/libtests/libtests.testcov b/libtests/libtests.testcov
index 2367ff6..f7c2bcf 100644
--- a/libtests/libtests.testcov
+++ b/libtests/libtests.testcov
@@ -1,9 +1,6 @@
 ignored-scope: qpdf
 Pl_LZWDecoder intermediate reset 0
-Pl_LZWDecoder last was table size 0
 Pl_ASCII85Decoder ignore space 0
-Pl_ASCII85Decoder read z 0
-Pl_ASCII85Decoder no-op flush 0
 Pl_ASCII85Decoder partial flush 1
 bits leftover 1
 bits bit_offset 2
@@ -41,22 +38,12 @@ QPDFArgParser read args from stdin 0
 QPDFArgParser read args from file 0
 QPDFArgParser required choices 0
 QPDFArgParser required parameter 0
-QPDFArgParser select unregistered table 0
-QPDFArgParser register registered table 0
-QPDFArgParser duplicate handler 0
 QPDFArgParser missing -- 0
 QPDFArgParser single dash 0
 QPDFArgParser help option 0
 QPDFArgParser positional 0
 QPDFArgParser unrecognized 0
 QPDFArgParser complete choices 0
-QPDFArgParser add reserved help topic 0
-QPDFArgParser add existing topic 0
-QPDFArgParser add to unknown topic 0
-QPDFArgParser duplicate option help 0
-QPDFArgParser bad option for help 0
-QPDFArgParser bad topic for help 0
-QPDFArgParser invalid choice handler to unknown 0
 JSON parse junk after object 0
 JSON parse invalid keyword 0
 JSON parse expected colon 0
diff --git a/libtests/qtest/qutil/qutil.out b/libtests/qtest/qutil/qutil.out
index a5f7b10..511a061 100644
--- a/libtests/qtest/qutil/qutil.out
+++ b/libtests/qtest/qutil/qutil.out
@@ -137,3 +137,8 @@ D:20210209191925Z
 done
 ---- memory usage
 memory usage okay
+---- error handlers
+caught exception: msg2
+caught exception: INTERNAL ERROR: msg4
+This is a qpdf bug. Please report at https://github.com/qpdf/qpdf/issues
+caught exception: msg6
diff --git a/libtests/qutil.cc b/libtests/qutil.cc
index 62cd9df..bb3eac2 100644
--- a/libtests/qutil.cc
+++ b/libtests/qutil.cc
@@ -3,6 +3,8 @@
 #include <qpdf/Pl_Buffer.hh>
 #include <qpdf/QPDFSystemError.hh>
 #include <qpdf/QUtil.hh>
+#include <qpdf/Util.hh>
+
 #include <climits>
 #include <cstdio>
 #include <cstring>
@@ -743,6 +745,29 @@ memory_usage_test()
     std::cout << "memory usage okay" << '\n';
 }
 
+void
+error_handler_test()
+{
+    qpdf::util::assertion(true, "msg1");
+    try {
+        qpdf::util::assertion(false, "msg2");
+    } catch (std::logic_error const& e) {
+        std::cout << "caught exception: " << e.what() << '\n';
+    }
+    qpdf::util::internal_error_if(false, "msg3");
+    try {
+        qpdf::util::internal_error_if(true, "msg4");
+    } catch (std::logic_error const& e) {
+        std::cout << "caught exception: " << e.what() << '\n';
+    }
+    qpdf::util::no_ci_rt_error_if(false, "msg5");
+    try {
+        qpdf::util::no_ci_rt_error_if(true, "msg6");
+    } catch (std::runtime_error const& e) {
+        std::cout << "caught exception: " << e.what() << '\n';
+    }
+}
+
 int
 main(int argc, char* argv[])
 {
@@ -782,6 +807,8 @@ main(int argc, char* argv[])
         is_long_long_test();
         std::cout << "---- memory usage" << '\n';
         memory_usage_test();
+        std::cout << "---- error handlers" << '\n';
+        error_handler_test();
     } catch (std::exception& e) {
         std::cout << "unexpected exception: " << e.what() << '\n';
     }